Updated at 4:58 p.m. ET
A gunman opened fire today at two military centers in Chattanooga, Tenn., killing four Marines and wounding three others.
The gunman is also dead, though it's unclear how that person was killed.
Law enforcement sources are telling NPR's Dina Temple-Raston the gunman is Mohammod Youssuf Abdulazeez, 24. No other information is known about him.
The FBI in a statement said the bureau's Knoxville Field Office, the Chattanooga Police Department and other law enforcement agencies are working jointly to investigate the shootings.
The shots were first fired at a military recruiting center on Lee Highway at about 10:45 a.m. ET. Police then pursued the shooter to the Navy Operational Support Center and Marine Corps Reserve Center Chattanooga on Amnicola Highway where the person opened fire again.
All those killed, including the attacker, were shot at the Navy building, FBI Special Agent in Charge Ed Reinhold said at a news conference. The entire incident lasted 30 minutes.
Rep. Mac Thornberry, R-Texas, chairman of the House Armed Services Committee, confirmed the victims were all Marines.
"Lives have been lost from some faithful people who are serving our country," Gov. Bill Haslam said, adding he was "sickened and saddened by this."
Reinhold said they believed the shooter was acting alone. The suspect, who is believed to be from the area, had numerous weapons, officials said at the news conference.
After initially saying the shootings were an "act of domestic terrorism," officials backtracked, saying all angles are being pursued as the motive is investigated.
A police officer who was shot in the ankle is being treated at a local hospital. Other individuals, including a Marine, also were injured and were treated. The Marine was later released.
This is a breaking news story. We'll update once we know more.