Chattanooga Mayor Andy Berke said five people died in all, including the gunman.
U.S. Attorney Bill Killian said officials were treating the attacks as an "act of domestic terrorism," though FBI Special Agent in Charge Ed Reinhold said authorities were still investigating a motive.
Two U.S. officials, speaking on condition of anonymity to discuss an ongoing investigation, told The Associated Press four U.S. Marines were among the dead. A soldier was being treated at a hospital for a gunshot wound to the leg, according to one of the officials. The other official said a police officer also was wounded.
There was also a shooting at a military recruitment center about 11 kilometres away.
Brian Lepley, a spokesman with the U.S. Army Recruiting Command in Fort Knox, Kentucky, said his recruiters there were told by law enforcement that the shooter, who was in a car, stopped in front of the facility, shot at the building and drove off.
The Army recruiters at the facility told Lepley they were not hurt and had evacuated; Lepley said he had no information about recruiters for the other military branches at the facility.
Sgt. 1st Class Robert Dodge, an Army recruiter in Chattanooga says he was at his office when someone opened fire and he heard 30 to 50 shots.
Marilyn Hutcheson, who works just across the street, said she heard a barrage of gunfire around 11 a.m.
"I couldn't even begin to tell you how many," she said. "It was rapid fire, like pow pow pow pow pow, so quickly. The next thing I knew, there were police cars coming from every direction."
She ran inside, where she remained locked down with other employees and a customer. The gunfire continued with occasional bursts she estimated for 20 minutes.
"We're apprehensive," Hutcheson said. "Not knowing what transpired, if it was a grievance or terroristic related, we just don't know."
