Four U.S. military personnel were killed in shootings Thursday at two military facilities in the southern state of Tennessee.
Officials said the gunman who opened fire at the two facilities was also killed in the incident. Several other people were injured, including a police officer.
Law enforcement sources said the shooter had been identified as Muhammad Youssef Abdulazeez. No other information about him was available.
Authorities said the gunman opened fire in a drive-by shooting at a military recruiting center at a shopping mall in Chattanooga where five branches of the military have adjoining offices. The Department of Defense said a Marine recruiter suffered a leg wound in the attack; he was treated at a hospital and released, according to Marine Corps officials.
Witnesses said they heard scores of shots, beginning about 10:30 a.m. Sgt. 1st Class Robert Dodge, 36, the leader for U.S. Army recruiting at the center, said he and his colleagues then got on the ground and barricaded themselves in a safe place.
Dodge said he did not see the shooter or a vehicle. The Army recruiting office was not damaged, but doors and glass were damaged at the neighboring Air Force, Navy and Marine offices, he said.
The gunman next drove to the Navy Operational Support Center and Marine Corps Reserve Center about seven miles away in a car described by witnesses as an open-topped Mustang. He unleashed what witnesses said was a barrage of gunfire.
The center sits in a light-industrial area. The two entrances to the fenced facility have unmanned gates and concrete barriers that require approaching cars to slow down to drive around them.
When the gunfire stopped, the shooter was found dead. Officials would not say whether he was shot dead or took his own life.
The Marine Corps confirmed that four Marines at the Navy/Marine reserve center were killed. Names were withheld pending notification of relatives.
"We are treating this as an act of domestic terrorism," Bill Killian, U.S. attorney for the Eastern District of Tennessee, said, though FBI Special Agent in Charge Ed Reinhold said authorities were still investigating a motive.
U.S. authorities increased security at federal facilities "out of an abundance of caution" after the shootings in Tennessee, U.S. Homeland Security Secretary Jeh Johnson said.
Johnson said in a statement that the Department of Homeland Security was closely monitoring the shooting and supporting the FBI investigation. He cautioned that "there are many unconfirmed and possibly false reports about events."
"Today was a nightmare for the city of Chattanooga," Mayor Andy Berke said. "As a city, we will respond to this with every available resource that we have."
"Lives have been lost from some faithful people who have been serving our country, and I think I join all Tennesseans in being both sickened and saddened by this," Gov. Bill Haslam said.
A White House spokesman said President Barack Obama has been briefed on the shooting and would continue to get updates.
Some information for this report came from Reuters.