Law enforcement sources have identified the shooter, who was wielding an AR-15 assault rifle and a handgun, as US citizen Omar Mateen, 29, from Port St. Lucie in Florida.
The gunman, who was born to Afghan parents, was carrying a suspicious device, possibly a suicide vest, when he opened fire on the dance floor inside Pulse in the early hours of this morning.
At least 50 people were killed and 53 others were injured in the shooting in the deadliest mass shooting in US history.
An FBI spokesman said the mass shooting is being investigated as an act of terrorism, adding that they are looking into whether this was an act of domestic or international terror, and if the shooter was a lone wolf.
The FBI believe the gunman, who was shot dead by officers, may have ‘leanings to radical Islamic terrorism’.
But his father, Mir Seddique, told NBC News his son became angry when he saw two men kissing in Miami several months ago.
‘This has nothing to do with religion,’ he said. ‘We are saying we are apologizing for the whole incident. We weren’t aware of any action he is taking. We are in shock like the whole country.’