Update Saturday 8:55 AM: In the year before the attack, the two did not slip entirely below the U.S. intelligence community's radar. The FBI said in a statement it interviewed alleged marathon bomber Tamerlan Tsarnaev in early 2011, after receving a tip from a foreign government official that Tamerlan was "a follower of radical Islam" and was preparing to leave the United States to join an underground organization. The FBI interviewed Tamerlan and his family, and conducted other checks, but "did not find any terrorism activity" at that time.
Update Saturday 8:05 AM: FBI and state/local investigators have started their investigation into whether the two Chechen brothers suspected of undertaking the Boston Marathon bombings acted alone, or had help.
Update 9 P.M.: Dzhokhar Tsarnaev has lost a lot of blood, a law-enforcement official told NBC.
Update 8:56 P.M.: Dzhokhar Tsarnaev has sustained a gunshot wound, Boston police told NBC.
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Update 8:53 P.M.: The Boston Globe's Jennifer Peter reported the mayor thanked police officers on the scanner. Police are now leaving Watertown en masse.
Update 8:52 P.M.: Dzhokhar Tsarnaev is being taken to the same hospital -- Mount Auburn Hospital in Cambridge -- where a transit police officer is recovering from a gunshot wound, the Boston Globe reported.
Update 8:46 P.M.: The Boston Police Department tweeted: "Suspect in custody. Officers sweeping the area. Stand by for further info."
Update 8:46 P.M.: CNN is also reporting police may have taken Boston Marathon bombing suspect Dzhokhar Tsarnaev into custody in Watertown, Mass., but this has not been confirmed.
Update 8:42 P.M.: NBC is reporting that the suspect is alive and in custody in Watertown. The police have called for a medic. A state trooper tells the media, "They got him, he's in custody."
Update 8:31 P.M.: The Boston Globe reported that three people in New Bedford, Mass., have been taken into custody in conjunction with the Boston Marathon terror-bombing investigation.
Update 8:16 P.M.: NBC is also reporting that Dzhokhar Tsarnaev is now holed up in a boat near Watertown, and that the police have him surrounded. The boat may be on fire.
Update 8:09 P.M.: CNN is reporting police apparently have cornered Boston Marathon bombing suspect Dzhokhar Tsarnaev in a small boat in the backyard of a home in Watertown, Mass.
Update 7:53 P.M.: A Massachusetts State Police representative, David Procopio, confirmed the activity in Watertown at this time is definitively related to the search for Dzhokhar Tsarnaev, according to the Associated Press.
Update 7:31 P.M.: CNN is reporting an emergency-services worker is carrying a child away from the area where Dzhokhar Tsarnaev is apparently cornered in Watertown, Mass. The reporter indicated the child may be OK, albeit scared.
Update 7:11 P.M.: CNN is reporting police apparently have cornered Boston Marathon bombing suspect Dzhokhar Tsarnaev in Watertown, Mass.
Update 7:09 P.M.: CNN is reporting a growing police presence on the streets of Watertown, Mass. Police are advising residents to stay in their homes.
Update 6:56 P.M.: CNN is reporting a couple of dozen rapid-fire gun shots have been heard on the streets of Watertown, Mass.
Update 6:47 P.M.: "Interpol has issued an international security alert, or Orange Notice, detailing the features of the improvised explosive devices used in the Boston Marathon bombings to assist law enforcement across its 190 member countries detect any similarly configured bombs," the International Criminal Police Organization said in a statement, as CNN noted. "The Interpol Orange Notice, requested by the U.S. authorities, contains photographs of the devices and identifying information including the fingerprints of the two suspects, 19-year-old Dzhokar Tsarnaev, currently being sought by authorities in the U.S., and his brother Tamerlan Tsarnaev, aged 26, who died after a shootout with police in Boston in the early hours of Friday."
Update 6:37 P.M.: CBS News has an interesting series of three tweets aboout Tamerlan Tsarnaev:
1. "JUST IN: FBI amends earlier assertion to Bob Orr that they had no prior contact with Tamerlan Tsarnaev, the bomb suspect killed in standoff."
2. "FBI now acknowledges they interviewed Tsarnaev 2 years ago at the request of a foreign country about possible extremist ties."
3. "They maintain that they did not find any derogatory information about him and closed the file. FBI expected to issue a statement shortly."
Update 6:23 P.M.: Pursuant to Massachusetts Gov. Deval Patrick's comment about certain restrictions being lifted in the Boston area, MBTA is reporting public transportation service -- buses and trains -- is in the process of being restored, subject to a number of advisories and alerts listed on its online site.
Update 6:05 P.M.: Col. Timothy Alben, superintendent of the Massachusetts State Police, said at a now-ongoing news conference that the Boston Marathon bombing suspect has not yet been apprehended. However, Massachusetts Gov. Deval Patrick said certain restrictions are being lifted so people not only in Watertown but also in Boston can begin going about their business, albeit with watchful eyes.
Update 5:27 P.M.: A purported cousin of the Boston Marathon bombing suspects repeatedly cautioned the younger, Dzhokhar Tsarnaev, about the elder, Tamerlan Tsarnaev, the Boston Globe reported. "I used to warn Dzhokhar that Tamaralan was up to no good," Zaur Tsarnaev, who identified himself as a 26-year-old cousin, told the Globe in a phone interview from Mkhachkala in the Russian republic of Dagestan. "[Tamarlan] was always getting into trouble. He was never happy, never cheering, never smiling. He used to strike his girlfriend. He hurt her a few times. He was not a nice man. I don’t like to speak about him. He caused problems for my family."
Update 5:12 P.M.: UMass Dartmouth brought its school-closing statement up-to-date Friday afternoon, saying: "Dartmouth will be closed Saturday, April 20. All students should evacuate campus immediately. Those who do not have transportation off campus should proceed immediately to Lot 1, where they will be transported to a secure location at Dartmouth High School, where accomodations are being made."
Update 4:47 P.M.: Violence apparently was a way of life for Tamerlan Tsarnaev and Dzhokhar Tsarnaev, according to a profile by the Associated Press. The former was an amateur boxer who had hoped to fight on the U.S. Olympic team, and the latter was a wrestler in high school, AP reported.
Update 4:18 P.M.: NBC Nightly News tweeted that seven improvised explosive devices have been found so far in Watertown and the Cambridge, Mass. home that was previously searched by police.
Update 4:01 P.M.: Boston's MBTA is reporting all public transportation service -- buses and trains -- remains suspended.
Update 3:59 P.M.: CBS News is reporting the 7-11 robbery in Cambridge, Mass., believed to have been connected to the Boston Marathon bombing suspects, was an unrelated incident. Fox 25 News Boston is reporting the Tsarnaev brothers went to a gas station but only purchased gas.
Update 3:44 P.M.: BBC reports the Tsarnaev brothers allegedly posted links to Islamic militant sites although New York Times states officials do not believe the Boston Marathon bombing suspects were linked to any militant groups.
Update 3:31 P.M.: In an interview with The Journal News, Alvi Tsarnaev, the Boston Marathon bombing suspects' uncle, said Tamerlan Tsarnaev called on Thursday and that it was the first time the two have spoken in two years. According to Alvi, “He said, ‘I love you and forgive me.’"
Update 3:14 P.M.: The Boston Red Sox have postponed their game against the Kansas City Royal. The game was scheduled to be played at Fenway Park at 7:10 P.M. The Boston Bruins have also postponed their game against the Pittsburgh Penguins. The game has been rescheduled for Apr. 20 at 12:30 p.m. at TD Garden.
Update 3:07 P.M.: Tamerlan Tsarnaev’s autopsy photo leaked online. Tsarnaev’s alleged death photo made its rounds on social media and was included in an internal email circulated by law enforcement officials.
Update 3:00 P.M.: President Barack Obama being briefed on the Boston Marathon bombing manhunt. In the photo are FBI Director Robert Mueller, Lisa Monaco, Assistant to the President for Homeland Security and Counterterrorism, Attorney General Eric Holder, Deputy National Security Advisor Tony Blinken and Vice President Joe Biden.
Update 2:35 P.M.: Mass. state police are cancelling the search for a 1999 green Honda Civic. Per the police, “Media reporting we are looking for a Honda Civic reg 116GC7, please note that we have that car. We are not looking for it. BOLO recalled.”
Update 2:26 P.M.: Boston Globe reporting that Tamerlan Tsarnaev was rushed to Beth Israel Deaconess Medical Center in Boston where doctors attempted to revive the Boston Marathon bombing suspect. Tsarnaev suffered massive injuries, including severe burns to the shoulder and chest as well as large torso wound, in the shootout with police in Watertown.
Tsarnaev was unconscious and handcuffed when police brought him to Beth Israel. Emergency crews and trauma teams from the hospital performed CPR on him and tried to revive him. Tsarnaev was pronounced dead at 1:35 a.m., reports Boston Globe.
Update 2:11 P.M.: Boston Police Department released a mock-up of the 1999 green Honda Civic that is currently being wanted in connection to the Boston Marathon bombing manhunt.
Update 2:10 P.M.: Dzhokhar Tsarnaev along with his father and mother became U.S. citizens in 2012, reports New York Times.
Update 1:51 P.M.: In a tweet sent out by Kadyrov, head of Chechen Republic, earlier on Friday, "And now they're going to kill the second one and then tell tales about how Kadyrov also planned to blow up the White House," in regards to early reports linking the Boston Marathon bombing suspects to Chechnya. In response to the discussion of terrorist ties, Putin's press secretary Dmitry Peskov stated, "President Putin stated when we were at war in Chechnya in the early 2000s, that we don't split terrorists into categories. There are no 'our' terrorists vs 'other' terrorists, you can't flirt with terrorists or categorize them. They all deserve equal condemnation'," reports BBC.
Update 1:47 P.M.: Conn. state police have issued a new statement saying they are looking for a 1999 green Honda Civic, reports NBC Connecticut.
Update 1:44 P.M.: The streets of Belmont have been cleared by police, reports Belmont Citizen-Herald.
Update 1:42 P.M.: A photo of the controlled blast being set up by the FBI that is scheduled for the afternoon on Norfolk Street.
Update 1:39 P.M.: WBUR is reporting 15 police office officers sustained injury early Friday morning in the firefight with the two Boston Marathon bombing suspects. The injured officers were treated at St. Elizabeth's Hospital in Brighton, Mass. for wounds tha included sprains, abraisions and bruises.
Update 1:31 P.M.: N.J. police have cordoned off an area of West New York, N.J. that includes the home of the alleged sister, Alina Tsarnaeva, of the Boston Marathon bombing suspects.
Update 1:25 P.M.: It is being reported NBC News Pete Williams said the man who was carjacked by the Tsarnaev brothers admitted to being the Boston Marathon bombers and they had shot a police officer at MIT.
Update 1:20 P.M.: Aunt of the two Boston Marathon bombing suspects, currently residing in Toronto, said she believes they are innocent, reports CBC. Maret Tsarnaeva said to CBC, "My nephews cannot be part of this terrible, horrible act that was committed in the streets of Boston." Tsarnaeva said the Tsarnaev brothers were "good kids" and was in disbelief that they were involved in the Boston Marathon bombing saying, "It's just not the case, it cannot be true."
Update 1:17 P.M.: Photo of Watertown police and SWAT team in armored car going door-to-door during the manhunt for the Boston Marathon bombing suspect.
Update 1:05 P.M.: Amtrak announced it has suspended service between Boston and New York
Update 12:58 P.M.: After several reports of false Twitter and Facebook accounts it is believed that Dzhokhar Tsarnaev's real Twitter account has been found.
Update 12:53 P.M.: It is being reported Dzhokhar Tsarnaev became a United States citizen on September 11, 2012 according to a federal official who spoke to CNN.
Update 12:51 P.M.: More details about the life of Boston Marathon bombing suspect Tamerlan Tsarnaev. In an interview with Bloomberg TV, the suspects' father said Tamerlan had a three-year-old daughter.
Update 12:45 P.M.: More from the press conference, Watertown Police Chief Edward Deveau said, "You’ve done great, you’ve done everything we’ve asked, but we need more time” Chief Deveau continued, “The Watertown community has always stood strong.” Col. Alben said no arrests have been made during the manhunt for the Boston Marathon bombing suspect currently at large. Mayor Menino said during the press conference, "We’re gonna get through this, we’re going to be a stronger city as we move forward," he continued, "We are not a city that lets terrorists win." Gov. Patrick urges all residents to respond only to uniformed police officers with proper identification as the manhunt for Dzhokhar Tsarnaev continues.
Update 12:38 P.M.: In the press conference, Gov. Patrick continues to urge residents to stay indoors. Massachusetts State Police Colonel Timothy Alben said police have been searching "door-to-door, street by street" in Watertown. Col. Alben also said there will be a controlled explosion on Norfolk Street in Cambridge, Mass. scheduled for the afternoon.
Update 12:29 P.M.: NBC Nightly News reports Boston Marathon bombing suspect Tamerlan Tsarnaev, 26, killed during the shootout in Watertown, had traveled to Russia from New York City's JFK Airport last year and spent six months in the country.
Update 12:22 P.M.: Governor and Boston Mayor Thomas Menino are en route to the press conference. Blackhawk helicopters in the sky are there for extra security.
Update 12:21 P.M.: A Syrian town shows support to Boston and the victims of the Boston Marathon bombing, reports Foreign Policy.
Update 12:19 P.M.: MTBA police officer Richard H. Donahue Jr. was wounded during the firefight in Watertown underwent surgery Friday morning and is currently in stable condition, reports 7News.
Update 12:05 P.M.: Former Mass. Senator, and current United States Secretary of State, John Kerry praised police response to the Boston Marathon bombing, "I think it is fair to say this entire week we have been in pretty direct confrontation with evil," Kerry continued, "In the past few days we have seen the best and we have seen the worst of human behavior and it is the best that all of us really want to focus on."
Update 11:57 A.M.: No updates regarding Boston Bruins and Boston Red Sox games scheduled for tonight. The Bruins and Pittsburgh Penguins canceled morning skates and will update regarding the status of Monday's game.
Update 11:54 A.M.: Boston Marathon bombing suspects' uncle quoted by AP as saying, "Turn yourself in, and ask forgiveness."
Update 11:49 A.M.: Reports indicate there is no traffic entering or exiting Watertown. All cars are subject to search if driving in surrounding area.
Update 11:43 A.M.: Boston's Logan Airport is open, with flights arriving and departing on schedule. Security has been heightened. Taxis are back in operation in the city of Boston.
Update 11:35 A.M.: Ramzan Kadyrov, head of the Chechen Republic, issued a statement in Russian on Instagram. Kadyrov said, "Any attempt to draw a connection between Chechnya and Tsarnaevs — if they are guilty — is futile. They were raised in the United States, and their attitudes and beliefs were formed there. It is necessary to seek the roots of this evil in America. The whole world must struggle against terrorism — that we know better than anyone else. We hope for the recovery of all the victims, and we mourn with the Americans."
Update 11:31 A.M.: WNYC is reporting there is no third suspect. Police are currently looking for Dzhokhar Tsarnaev who remains at large. Boston Globe notes police are searching a radius of 20 blocks in Watertown.
Update 11:19 A.M.: Amtrak has several service changes stemming from the manhunt for the Boston Marathon bombing suspect currently at large. Per Amtrak's statement, "Amtrak Acela Express and Northeast Regional service is suspended indefinitely between Providence, RI and Boston. Amtrak Downeaster is operating a modified schedule with no service to Boston," the statement continues, "Amtrak service is operating normally between Washington, DC, Philadelphia and New York. The Springfield Shuttle between New Haven, Conn. and Springfield, Mass. is also operating on a normal schedule."
Update 11:17 A.M.: More updates about recovered Honda CRV. Car was found in Cambridge, Mass. reports New York Times.
Update 10:56 A.M.: The recovered Honda CRV was abandoned, reports Boston Globe. Police believe Tsarnaev left the vehicle and is currently on foot.
Update 10:50 A.M.: Police believe house currently being surrounded may be booby trapped, reports NBC Nightly News. WCVB is reporting there is a potential bomb threat on Arsenal Street and the street is being backed off by police.
Update 10:49 A.M.: UMass Dartmouth updated about the school closing stating, "This action is in response to information that the person being sought in connection with the Boston Marathon bombing is a registered student."
Update 10:44 A.M.: Robin Young, radio host of "Here and Now," tweeted a photo of her nephew with Boston Marathon bombing, Dzhokhar Tsarnaev, during graduation. Young's nephew has been cropped out.
Update 10:39 A.M.: WCVB is reporting that no one of interest was inside the Honda CRV police recovered.
Update 10:33 A.M.: Boston Police released a mock-up of the license plate of the gray Honda CRV wanted in conjunction with the Boston Marathon suspect at large. Connecticut officals are confirming the vehicle has been recovered.
Update 10:26 A.M.: Photo of Humvees in Watertown as police continue to search for Boston Marathon bombing suspect currently at large.
Update 10:22 A.M.: University of Massachusetts Dartmouth campus has been closed.
Update 10:07 A.M.: Norwich Bulletin has more updates about the Honda CRV. According to the report, "Police are searching for a gray Honda CRV, with Massachusetts license plate 316-ES9." Connecticut and Massachusetts police believe the vehicle may be occupied by Dzhokar Tsarnaev, the Boston Marathon bombing suspect currently at large. It is believed that the suspect may be headed to New York.
Update: 10:04 A.M.: Boston hospitals are currently in lockdown, reports Boston Globe. Patients cannot leave and hospitals are only admitting patients coming in via ambulances.
Update 9:57 A.M.: More details about Tamerlan Tsarnaev, the Boston Marathon bombing suspect who was killed. The suspect was a boxer and had competed at the National Golden Gloves competition in Salt Lake City, Utah. The older brother was a subject of a photo essay by Johannes Hirn entitled "Will Box For Passport."
Update 9:54 A.M.: The campus officer killed at MIT has been identified as Sean Collier.
Update 9:52 A.M.: Reports indicate the Amtrak train was given the all clear.
Update 9:50 A.M.: New York Magazine editor Justin Miller indicates a third suspect in the Boston Marathon bombing, in addition to the Tsarnaev brothers, may have been on an Amtrak train headed to New York. Police have stopped the train and are currently investigating. Train was heading from Boston to New York and was stopped in Norwalk, Conn.
Update 9:39 A.M.: Your Anon News, via NBC, is reporting that Connecticut police have asked for an APB on a Honda CRV.
Update 9:34 A.M.: In a possibly unrelated incident, WGRZ is reporting two Russian nationals were arrested near Niagara Falls. Inside the car there were four suspicious backpacks and a bomb squad has been called in. The FBI know about situation in Niagara Falls.
Update 9:31 A.M.: Boston police scanners live streams have stopped broadcasting online. Prior to the scanners going offline, police were heard saying the Boston Marathon bombing suspect was wearing a suicide vest.
Update 9:26 A.M.: In an interview with CNN, the suspects' uncle had not spoken to the brothers in two years although the older brother, Tamerlan Tsarnaev who was killed in Watertown, had called him on Thursday.
Update 9:21 A.M.: The FBI has released a new photo of the Boston Marathon bombing suspect currently at large.
Update 9:12 A.M.: Associated Press interview father of the Boston Marathon bombing suspects. The father was quoted as saying of Dzohokhar Tsarnevk, "Is accomplished medical student and 'a true angel'."
Update 9:11 A.M.: Police on scanner are heard saying posted online "I will kill all of you as you killed my brother."
Update 9:04 A.M.: BBC Moscow has more details about Dzhokhar Tsarnevk. According tot the report, the Boston Marathon bombing suspect was born in Kyrgyzstan and moved with his family to Makhachkala, capital of Dagestan, a southern Caucasus Republic located near Chechnya. Tsarnevk moved to the United States in either 2001 or 2002.
Update 9:00 A.M.: Boston Globe reporter Wesley Lowery reports two suspects were taken into custody from the believed apartment of the suspects located on Norfolk Street.
Update 8:52 A.M.: Jeff Bauman helped identify the two suspects involved in the Boston Marathon bombing. In an interview with Bloomberg, Bauman said, after waking up from emergency, he asked for a pen and reported one of the suspects had looked directly at him moments before the explosion.
Update 8:47 A.M.: Police have surrounded a residence on Willow Park in Watertown, reports Boston Globe. SWAT team and armored car have arrived on scene near the intersection of Quimby and Willow Park. Police are calling out to the house using speakers, notes the Globe.
Update 8:45 A.M.: Alleged profile of Dzhokhar Tsarnaev on VK, Russia's Facebook.
Update 8: 40 A.M.: According to Los Angeles Times' Richard Serrano, FBI sources said they found blood spots while searching for Dzhokhar Tsarnaev, indicating he may have been wounded.
Update 8:34 A.M.: Taxi service in the city of Boston has been suspended. Associated Press is reporting the suspect's unvcle has confirmed they are brothers. Reports indicate the two suspects are from the Russian Caucasus region, which includes Chechnya.
Update 8:27 A.M.: An alleged photo of Dzhokhar Tsarnaev seen next to Martin Richard, the eight-year-old who was killed in the Boston Marathon bombing on Monday.
Update 8:25 A.M.: Massachusetts Institute of Technology (MIT) have announced classes have been canceled for the day and urges, "Following State guidance, MIT asks employees not to come to MIT today. Stay home and indoors. Students should stay in residences." Boston University is also closed which includes Boston University Medical Campus will be closed today, due to the ongoing police search for the second suspect in the Marathon bombing. This includes the Henry M. Goldman School of Dental Medicine, School of Public Health, School of Medicine and Division of Graduate Medical Sciences.
Update 8:16 A.M.: Reports indicate Harvard University and Cambridge College are locked down. Residents of Watertown, Cambridge, Waltham, Newton and Belmont are being asked to stay inside. Parents are being asked to not send their children to school.
Update 8:11 A.M.: Press conference was held in Watertown, Mass. Governor of Massachusetts Deval Patrick announced a "massive manhunt" is currently underway and confirmed one suspect was killed, reports the Boston Globe.
Update 8:06 A.M.: Boston Regional Intelligence Center released a new poster of Dzhokhar Tsarnaev, the Boston Marathon Bombing currently at large. According to BBC, officials are asking residents of Watertown and neighboring towns to stay indoors and any individuals in public areas are being urged to return home. Police are currently investigating areas of Watertown as well as previously searched neighborhoods.
Update 8:01 A.M.: Via Twitter, a view from Watertown as police continue the manhunt for Dzhokhar Tsarnaev.
Following a robbery at a 7-11 and fleeing to MIT, two Boston Marathon bombing suspects, identified as Tamerlan Tsarnaev And Dzhokhar Tsarnaev, 19, shot a campus police officer before heading to Watertown, Mass.
In Watertown, the two brothers had a standoff with police officers, which included reports of the two suspects allegedly throwing an explosive device at the officers on scene. There was a firefight between the suspects and Boston and Watertown police. One suspect, Tamerlan Tsarnaev, was reportedly killed during the shootout, allegedly in an explosion from a bomb he was carrying, while Dzhokhar Tsarnaev remains at large.
Dzhokhar Tsarnaev is currently at large. Watertown police have shut down street where the suspect's apartment was on. Massachusetts Bay Transportation Authority (MBTA) bus and train service has been suspended.