Crowds scrambled for their lives last night when a gunman opened fire on a music festival in Las Vegas killing at least 50 people.

The shooter fired 200 rounds from a room on the 32^nd floor of the Mandalay Bay onto the terrified crowd below at 10:08pm. At least 400 have been injured in what is now the deadliest mass shooting in American history.

Authorities have identified the shooter as 64-year-old Stephen Paddock, who investigators say was found dead from suicide after police breached his room.

They are working to establish a motive and his home in nearby Mesquite, Nevada, was being searched Monday morning. Authorities have ruled out involvement by the woman he was sharing the home with, Marilou Danley, after authorities made contact with her on Monday morning and found her out of the country. 

Witnesses described the chaos and panic of the moment as the crowds struggled to flee to safety, and the confusion that reigned in the first moments of the attack as the popping sounds were mistaken by some as fireworks or fire crackers.

The gunfire started while country music star Jason Aldean was performing on set at the Route 91 festival.

Pope Francis has called the attack a 'senseless tragedy.'

'Deeply saddened to learn of the shooting in Las Vegas, Pope Francis sends the assurance of his spiritual closeness to all those affected by this senseless tragedy,' said a message sent to the Roman Catholic bishop of the Nevada city on Monday.

Aldean posted an emotional message on his Instagram page after the shooting last night with a 'Pray for Las Vegas' image.

'Tonight has been beyond horrific. I still dont know what to say but wanted to let everyone know that Me and my Crew are safe,' he said.

'My Thoughts and prayers go out to everyone involved tonight. It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night. #heartbroken#stopthehate'