There were more than 300 people in the popular nightclub when he opened fire and many who heard the first gunshots believed they were part of the music.

"All you saw is people running and screaming and there were bodies in the parking lot where bodies were being tagged," club-goer Christopher Hansen told CNN. "It was like a scene from a horror movie."

One mother told of how her murdered son's heartbreaking last texts to her read: “Mommy I love you ... In club they shooting.”

Mina Justice's 30-year-old son Eddie was trapped in the club's toilets as the gunman fired out shots from an AR-15 assault rifle and a handgun.

“He’s coming I’m gonna die,” the terrified man wrote. He was confirmed to have died this morning.

More than 50 people have been injured in the shooting, many seriously.

In Orlando, blood banks have been overwhelmed by people queuing up to make donations to help the injured.

"You want to do something to help," Frank Tiffany, 69, told the Orlando Sentinel, as he waited in line with hundreds of others. "It's hard to believe ...You have to do something to help. You can't stay home."

Making a stand against hate: UK unites to support Orlando