Clark County Sheriff Joseph Lombardo confirmed that the suspected gunman was a 64-year-old man named Stephen Paddock.
“As far as his history and his background, we haven’t completed that part of the investigation yet,” Mr Lombardo said, adding that police “located numerous firearms in the hotel room that he occupied”.
Officers are currently at his residence.
NBC News reported that Paddock was a white man from Mesquite, Nevada. According to other reports he had previously lived in California and Florida.
Earlier, Mr Lombardo had said that they believed the gunman was a “lone wolf”.
”We have no idea what his belief system was,” he said.
“Right now, we believe he was the sole aggressor and the scene is static.
“The dead man lived locally and his motives are not known.
“There were no explosives involved in the attack but police used a controlled explosion to get to the suspect.”
Police are “confident but not 100 per cent sure” that they have located Marilou Danley, a 62-year-old woman who it is believed travelled with Paddock before the attack.
They have also found two vehicles that were being searched for in connection with the shooting.
Mr Lombardo confirmed that at least 50 people were killed and a further 200 were injured after the gunman opened fire from the 32nd floor of the Mandalay Bay hotel in Las Vegas.
He took aim at a crown enjoying the Route 91 Harvest country music festival.
The updated death toll makes the attack the deadliest mass shooting in US history.
This is a breaking news story. More to follow.