Four U.S. Marines were killed Thursday after dozens of shots were fired by a lone gunman at a Navy Reserve training facility in Chattanooga, Tennessee, officials said. The gunman, who began his two attacks around 10:45 a.m. EDT at a recruiting center in a strip mall before driving around 5 miles to the training facility, was shot dead by local police.

CNN reported that the alleged gunman's name is Muhammad Youssef Abdulazeez, citing two sources familiar with the ongoing investigation. 

President Barack Obama expressed his "deepest condolences" to the families of the Marines, whose names have not yet been released. The president said the killer "appears to be a lone gunman." He said officials are working to ensure that "all our defense facilities are properly attentive and vigilant as we sort through what happened." 

William C. Killian, U.S. Attorney for the Eastern District of Tennessee, said that the shooting was being treated as an "act of domestic terrorism."

Chattanooga Mayor Andy Berke said the incident "is a nightmare for the city of Chattanooga."

FBI Knoxville chief Ed Reinhold, who distanced himself from Killian's comments that the shooting was an act of domestic terrorism, said that shooter was a local resident and that the FBI was not expecting the attack. "We believe the suspect was residing in the area prior to this events," he said. "We had no intelligence there would be any kind of attack today."

Officials said the two incident were over within 30 minutes and that the FBI had taken over the investigation. Authorities ordered a lockdown for area businesses and schools.  

Pictures taken by witnesses and broadcast by TV networks showed two to three dozen bullet holes in the glass of the recruiting center, but very few in the private businesses on either side, indicating that it was a targeted attack against military personnel. 

The shooter, who police believe was acting alone, drove a black BMW, leading some news outlets to speculate initially that two gunmen in different vehicles were involved. Police at the news conference have confirmed that the shooter was alone. 

A temporary no-fly zone was activated in the area.

The mayor told reporters in the immediate wake of the shootings that "this is a very, very terrible situation."

The news comes two weeks after the Washington Navy Yard was placed on lockdown after an active shooter was reported in the facility. It was later determined to be a false alarm.