Authorities says the Pulse shooter previously was suspected of having ties with terrorism.
Ron Hopper of the FBI says Omar Mateen was investigated in 2013 and 2014 and interviewed multiple times. He was not under investigation at the time of the shooting.
"Mateen made calls to 911 this morning in which he stated his allegiance to the leader of the Islamic State", said Hopper. "We are looking into any and all connections both domestic and international."Authorities say Mateen legally bought at least two weapons days before the shooting. They say the Fort Pierce man was 29 and born in New York.
Fifty are dead and 53 are injured after the overnight shooting, the worst shooting in American history. Authorities say the death toll likely will rise.