Mass shooting at Tennessee military facilities will be investigated as domestic terrorism

Shootings at a pair of military facilities in Chattanooga, Tenn., Thursday, left five people dead, including four Marines and the lone gunman, officials said.

"It is incomprehensible to see what happened," Chattanooga Mayor Andy Berke said at a news conference Thursday afternoon. "This is a nightmare for the city of Chattanooga."

Three other people, including a Chattanooga police officer, were wounded in the shootings, Berke said. They were transported to local hospitals with non-life-threatening injuries.

The shootings began shortly after 10:30 a.m. at a National Guard office in a strip mall on Lee Highway. A witness there described hearing as many as 20 shots fired there before the gunman fled. A photo posted to Facebook by a witness shows the door of the office littered with bullet holes.

The shooter then drove 7 miles to the Chattanooga naval reserve center, where a witness told CNN she saw a man with "a high-powered rifle" fire multiple shots from a convertible silver Mustang into recruiting offices at the center shortly before 11 a.m. ET.

Four U.S. Marines were killed at the naval center, Pentagon officials told CNN. Their names have yet to be released.

The gunman, who has yet to be publicly identified, was killed at the scene.

"This individual brutally and brazenly attacked members of our armed forces," Chattanooga Police Chief Fred Fletcher said at the news conference. He declined to speculate on a motive.

Because the shootings occurred at U.S. military facilities, the FBI is leading the investigation.

U.S. District Attorney William C. Killian said officials were treating the shootings "as an act of domestic terrorism."

But Ed Reinhold, special agent in charge of the FBI's Knoxville field office, said at this point there is no evidence to suggest it was.