Police are struggling to find a motive for America’s worst ever shooting massacre after identifying 64-year-old retiree Stephen Paddock as the man responsible.

Paddock, who lived in a retirement community in Mesquite, Nevada,  had no criminal record and was not believed to be connected to any militant group.

The former accountant took his own life after firing an automatic weapon from the window of his Mandalay Hotel room, killing at least 59 people and wounding more than 527 others.

Police said Paddock killed himself before they entered the hotel room he was firing from.

Clark County Sheriff Joseph Lombardo told reporters investigators had no information about Paddock’s motive.

“We have no idea what his belief system was,” Sheriff Lombardo said. “I can’t get into the mind of a psychopath.”

Federal officials said there was no evidence to link Paddock to international militant groups.

“We have determined to this point no connection with an international terrorist group,” FBI special agent in charge Aaron Rouse told reporters.

US officials discounted a claim of responsibility for the attack made by Islamic State, through its Amaq news agency.

“The intelligence community is aware of the claim of responsibility by a foreign terrorist organisation for the shooting in Las Vegas,” CIA spokesman Jonathan Liu said in an email. “We advise caution on jumping to conclusions before the facts are in.”

Just in: new image of the home of Las Vegas shooting suspect Stephen Paddock after police ripped off the garage door to execute warrant #abc pic.twitter.com/l2Ll9X9GNh

— Kenneth Moton (@KennethMoton) October 2, 2017

One US official said there was reason to believe that Paddock had a history of psychological problems.

Sheriff Lombardo said there were more than 10 rifles in the room where Paddock killed himself. He had checked into the hotel on Thursday.

Police found several more weapons at Paddock’s home in Mesquite, about 145 km northeast of Las Vegas, Mesquite police spokesman Quinn Averett told reporters.

“He brutally murdered more than 50 people and wounded hundreds more. It was an act of pure evil,” US President Donald Trump said in a White House address.

A female companion of Paddock remains a person of interest in the mass shooting at a concert on the Las Vegas Strip that killed at least 58 people and wounded more than 515.

Sheriff Lombardo said Marilou Danley, reportedly an Australian citizen, was not in the US when Paddock began shooting from the 32nd floor of the Mandalay Bay casino.

Authorities initially released Ms Danley’s driver’s licence photo and descriptions of two cars.

“We still consider her a person of interest,” Sheriff Lombardo said.

“We have been in contact with her and we plan to engage her upon her return to the country.”

Police wish to speak to a woman named Marilou Danley. Photo: LVPD

Mr Trump ordered flags lowered to half-mast in a national gesture of mourning and said he would visit Las Vegas on Wednesday.

The shooting broke out on the final night of the three-day Route 91 Harvest Festival, a sold-out event featuring top acts such as Eric Church, Sam Hunt and Jason Aldean.

The suspected shooter’s brother, Eric Paddock, said the family was stunned.

Eric Paddock told US media his brother had worked as an accountant and had plenty of money.

“He was a wealthy guy playing video poker … going on cruises,” he said, adding that his brother could afford anything he wanted.

Paddock’s father was a well-known bank robber and at one point was on the FBI’s 10 most wanted list, he said. Their father died a few years ago.

Eric Paddock said his brother had been married in the past and lived with his girlfriend, but he didn’t know of any children.

He said they last communicated via a text message more than a week ago when Stephen Paddock asked about their mother who’d lost power during Hurricane Irma.

Eric Paddock said he has no idea why his brother would kill anybody and found out about the shooting when police called to inform his family.

Las Vegas shooter's brother Eric Paddock speaks out: "It makes no sense" https://t.co/Xolt9gNEdb pic.twitter.com/fX5sn6NdQu

— Variety (@Variety) October 2, 2017

– With agencies