Chattanooga shootings: A gunman killed 4 Marines at Tennessee US Navy centres

A gunman attacked two military sites in Chattanooga, Tennessee killing Four Marines, on Thursday, the U.S. Navy said.

The 24-year-old suspected shooter, Mohammod Youssuf Abdulazeez, was killed, the FBI said.

Investigators "have not determined whether it was an act of terrorism or whether it was a criminal act," Ed Reinhold, FBI special agent in charge, told reporters. "We are looking at every possible avenue, whether it was terrorism -- whether it was domestic, international -- or whether it was a simple, criminal act."

U.S. Attorney Bill Killian earlier told reporters that authorities were treating the shooting as an "act of domestic terrorism."