UPDATE [3:05 P.M.]Sources tell CNN that the alleged shooter's mother was a teacher at Sandy Hook Elementary School and was allegedy shot and killed by her own son.
UPDATE [3:05 P.M.]Source tells the Associated Press that the younger brother of alleged Connecticut school shooting suspect Ryan Lanza is being held.
UPDATE [2:17 P.M.] Investigators told CBS News that a body has been found at the home of alleged shooting suspect, Ryan Lanza.
UPDATE [2:12 P.M.]Sources tell a CNN correspondent that the number of people killed in the shooting at Sandy Hook Elementary School in Newtown, Conn., is now closer to 30, most being children.
UPDATE [12:40 P.M.]Federal and local officials have confirmed to ABC News that dozens of students and teachers have been shot and killed in a shooting at the Sandy Hook Elementary School in Newtown, Conn.
UPDATE [12:15 P.M.] An eyewitness, who was in a meeting regarding a Sandy Hook student at the time of the shooting, has told CNN's managing editor that the incident took place in a school hallway, and that the alleged shooter fired off at least 100 rounds.
Furthermore, according to the eyewitness, when three people exited the meeting room, to investigate the loud noises, only one person returned. Details are still emerging on this breaking news story.
UPDATE [12:05 P.M.] CBS News is reporting that at least one child is dead following a shooting at Sandy Hook Elementary in Newtown, Conn.
UPDATE [11:57 P.M.] Three people have been transported to a nearby hospital in Danbury, Conn., following a shooting at Sandy Hook Elementary in Newtown. Two handguns, believed to belong to the shooter, have also been recovered from the scene.
Multiple news outlets are reporting that a shooting occurred at Sandy Hook Elementary in Newtown, Conn., on Friday. While details on this breaking news story are scarce at the moment, state police sources told the Hartford Courant that one shooter is dead. Earlier reports of a second shooter are unconfirmed.
"Due to reports of a shooting as yet unconfirmed, the district is taking preventive measures by putting all schools in lockdown until we ensure the safety of all students and staff," Kathy June, Newtown Public School District's secretary of the superintendent, said in a statement, obtained by ABC News.
According to the Hartford Courant, police reported that a shooter was in the main office of the school shortly after 9:40 a.m. A person in one room had “numerous gunshot wounds,” police said.
Additional updates from the scene at Sandy Hook indicate that dozens of state troopers are assisting local police and a number of stretchers are set up.
All public and private schools in the town are on lockdown as state police have units en route to Newtown following reports of the shooting.
Check back for real-time updates on this breaking news story.