Orlando shooting: Witnesses film the firefight between gunman and police

Bystanders have witnessed the distressing scenes of first responders' frantic attempts to take down the gunman who murdered at least 50 inside an Orlando nightclub.

Amateur footage from outside the venue of a gun battle between US police and Mateen has been posted online this morning by witness Anthony Torres.

"Oh my God, they’re all shooting back at each other," Torres can be heard saying as he films the scenes in front of him.

As he continues to film, dozens of police cars and ambulances descend on the scene, their sirens blazing silently.

The voice of a female officer pierces the quiet.

"We need more… we need more (force) up here… we need to get people to the hospital," she can be heard saying amid sudden blaring sirens.

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Torres and his sister and friends had walked out of the club just seconds before the massacre began.

He took to Facebook after recognising one of the men confirmed killed in the shooting.

"This guy was with us in the VIP and him and his friends where having such a good time he was so happy and seeing this has really hurt my heart," Torres wrote about Stanley Almodovar III.

"How can such happiness and good times turn in to this in a matter of seconds."

In another video posted on Snapchat two bystanders witness the same succession of bullets firing from a different angle.

"Oh my God, people are getting shot," one of the men said.