New bodycam footage from the Pulse nightclub shooting in Orlando, Florida, has been released, showing the moment police confronted the shooter.

It was the deadliest mass shooting in US history by a single gunman, killing 49 people and injuring 53.

Eleven hours of footage was made available to ABC and the Orlando Sentinel.

The graphic footage shows police entering the club as patrons run outside away from the automatic gunfire, which can be heard in the background of the video.

Police can be heard asking if people were hurt and checking pulses on victims as they moved through the scene, but had to wait for the shooter to be located before being able to help.

“A person reached up and asked for help, but at that point we didn’t know where the shooter was, if he was detained, if he was deceased, or what was going on,” Kyle Medvetz, one of the police officers who responded, told ABC News.

When they identified the location of the shooter, later identified as Omar Mateen, one officer said: "Come out with your hands up, or you will die."

What ensued was a harrowing three-hour standoff during which Mateen, 29, called himself an "Islamic soldier" and hid in a bathroom with several hostages. He also said: “I pledge my allegiance to Baghdadi on behalf of the Islamic State,” in a reference to the leader of the Isis terror group Abu Bakr al-Baghdadi.

Police did not immediately storm the club after it turned into a hostage situation because Mateen claimed there were vehicles outside of the club that contained bombs. He also claimed he was wearing a vest strapped with explosives.

“During that whole three hours, we were in there saving people from the dance floor, from dressing rooms, from the other bathroom,” Orlando Police Chief John Mina told ABC News.

The standoff ended with police killing Mateen.

The video also shows the aftermath of the shooting, with one officer saying there would be "astronomical numbers" of dead and injured.

The FBI confirmed that Mateen had been investigated twice before because he said he hoped to "martyr himself". However, not enough evidence was found to charge him with anything.

Then-Director James Comey said Mateen told agents that his colleagues were harassing him because he was Muslim and that is why he made the comment.