The man who killed 59 people and injured 527 others in a mass shooting in Las Vegas was a big-spending gambler who took 23 guns into his hotel room before opening fire on crowds attending an outdoor music festival.

Map locates shooting in Las Vegas(PA Graphics)

Stephen Craig Paddock sprayed bullets on revellers enjoying the Route 91 Harvest Festival from the 32nd floor of the Mandalay Bay Hotel and Casino on Las Vegas Strip.

The 64-year-old retired accountant from Mesquite, Nevada, killed himself before officers stormed Room 135 in the gold-coloured glass skyscraper.

Investigators work at the scene(Chris Carlson/AP)

Assistant sheriff Todd Fasulo said Paddock had 23 guns — some with scopes — in his hotel room.

Authorities found 19 more guns at his home in Mesquite, as well as explosives and thousands of rounds of ammunition.

Several pounds of ammonium nitrate, a fertiliser that can be turned into explosives such as those used in the 1995 Oklahoma bombing, were discovered in his car.

Stephen Paddock's home in Reno, NevadaStephen Paddock’s home was searched by the FBI (Scott Sonner/AP)

Investigators believe the shooting – the most deadly in modern US history – was a “lone wolf” attack, and say they do not have any information to lead them to suspect there were more assailants.

Deadliest mass shootings in US history(PA Graphics)

His father was a bank robber who was once on the most wanted list.

Benjamin Hoskins PaddockBenjamin Hoskins Paddock escaped from a federal prison in Texas in 1969, following a conviction for a string of bank robberies in Arizona. (Charlie Nye/The Register-Guard via AP)

Investigators are working to establish a motive for the attack, but a law enforcement official said there was no immediate indication that the massacre was connected to international terrorism.

The Islamic State group claimed responsibility for the attack and said the gunman was “a soldier” who had converted to Islam months ago, but it provided no evidence to back up the claim.

A graphic released by Amaq <a href=News Agency, a media arm of the Islamic State group, claiming responsibility for the mass shooting in Las Vegas">A graphic released by Amaq News Agency, a media arm of the Islamic State group, claiming responsibility for the mass shooting in Las Vegas (Amaq News Agency via AP)

Country music star Jason Aldean was performing on Sunday night at the end of the three-day festival in front of a crowd of more than 22,000 when the gunman opened fire from inside the 44-floor hotel across the street.

Paddock had checked into the hotel room on Thursday, authorities said.

People attending the country music concert described scenes of horror as they realised that what they first thought were fireworks were actually gunshots.

A woman cries while hiding inside the Sands Corporation plane hangar after the shootingA woman cries while hiding inside the Sands Corporation plane hangar after the shooting (Powers Imagery/AP)

Harrowing video footage showed Aldean stopping his performance after an initial volley of shots could be heard.

After a pause, the gunman fired another volley, with the muzzle flashes visible from the casino as victims fell to the ground, while others fled in panic.

Concertgoers fled into casinos and crammed into cars to get away from the shooting.

A young woman hides inside the Sands Corporation plane hangar after the shooting(Powers Imagery/AP)

Police shut down busy Las Vegas Boulevard, and federal and state authorities converged on the scene.

Interstate 15 was briefly closed, and flights at McCarran International Airport were suspended.

Hospital emergency rooms were jammed with the wounded.

The dead included at least three off-duty police officers from various departments who were attending the concert, authorities said.

Two on-duty officers were wounded, one critically, police said.

Assistant sheriff Fasulo said Paddock shot a security guard on the 32nd floor of the Mandalay Bay Hotel.