Nightclub massacre gunman Omar Mateen was gunned down as he tried to flee the scene of the shooting through a hole punched in a wall by a police armoured vehicle, authorities have revealed.
US authorities are investigating whether anyone helped Mateen to massacre 49 people at Orlando's Pulse gay nightclub, but say they do not believe anyone connected to the shooting posed a current danger to the public.
The rampage began about 2:00am on Sunday (local time) as the club was packed with some 350 people. Many fled as the gunman raked the crowd with bullets from an AR-15-style semiautomatic rifle and a pistol.
An initial wave of officers charged into the club and trapped Mateen in a bathroom, Orlando Police Chief John Mina told reporters.
That allowed many patrons to flee, although others were trapped in the restroom with Mateen, leading to a stand-off.
"We were able to save and rescue dozens and dozens of people," Chief Mina said.
Police negotiated with Mateen for about three hours before calling in a BearCat armoured vehicle which broke a hole in the wall, allowing hostages to escape.
Mateen also emerged from the hole and was shot to death by officers, police said.
FBI director James Comey said there were "strong indications" Mateen had been radicalised, in part through the internet, but federal authorities were still working to determine his exact motives.
Mr Comey said the FBI saw no indication the attacker had been part of any kind of network and it was not clear which terrorist group he supported.
During phone calls with authorities in the middle of the shooting rampage, Mateen mentioned support for the leader of Islamic State, the Boston Marathon attackers and a Florida man who became an Al Nusra Front suicide bomber in Syria, Mr Comey said.
Al Nusra is an Al Qaeda offshoot at odds with Islamic State.