THE Las Vegas gunman’s girlfriend is being quizzed by police as they attempt to find out why a man with no record of violence or crime would kill 59 people and leave 527 others injured after opening fire on a concert crowd from a high-rise hotel.

Stephen Paddock’s girlfriend Marilou Danley, 62, who was in the Philippines at the time of the shooting, was met by FBI agents after she touched down in Los Angeles.

Sheriff Joseph Lombardo, who has called Danley a “person of interest” in the attack, said: “We anticipate some information from her shortly.”

He said he is “absolutely” confident authorities will find out what set off Paddock, a 64-year-old high-stakes gambler and retired accountant who killed himself before police stormed his 32nd-floor room at the Mandalay Bay Hotel and Casino.

Paddock had opened fire on a 22,000-strong crowd at the outdoor Route 91 Harvest Festival, during a performance by country music star Jason Aldean.

Danley first arrived in the Philippines on September 15, according to immigration documents.

She departed on September 22 then returned three days later on a flight from Hong Kong. She was travelling on an Australian passport.

Danley’s Australia-based sisters believe Paddock sent her away to prevent her from interfering with his plans.

Australia’s Channel 7 TV network interviewed the sisters with their faces obscured and their names withheld. They said they believe their sister could not have known about his ideas.

One of the women said Danley is “a good person” who would have stopped Paddock had she been there.

Another of the sisters, who live near Brisbane, Queensland, said they believed Marilou knew Paddock had guns, but not as many as he had.

Paddock transferred $100,000 to the Philippines in the days before the shooting, a US official said.

Investigators are still trying to trace that money and looking into a least a dozen financial reports over the past several weeks that showed Paddock gambled more than $10,000 per day, the official said.

As for what may have set Paddock off, retired FBI profiler Jim Clemente speculated that there was “some sort of major trigger in his life – a great loss, a break-up, or maybe he just found out he has a terminal disease”.

Clemente said a “psychological autopsy” may be necessary to try to establish the motive.

If the suicide did not destroy Paddock’s brain, experts may even find a neurological disorder or malformation, he said.

He said there could be a genetic component to the slaughter: Paddock’s father was a bank robber who was on the FBI’s most-wanted list in the 1960s and was diagnosed as a psychopath.

“The genetics load the gun, personality and psychology aim it, and experiences pull the trigger, typically,” Clemente said.

Paddock had no known criminal record, and public records showed no sign of financial troubles.

His brother, Eric Paddock, said he was at a loss to explain the massacre.

“No affiliation, no religion, no politics. He never cared about any of that stuff,” he said outside his Florida home.

Eric Paddock said his brother did show a confrontational side at times. He apparently hated cigarette smoke so much that he carried around a cigar and blew smoke in people’s faces when they lit up around him.

At least 45 patients at two hospitals remain in a critical condition. All but three of the dead had been identified by Tuesday afternoon, Sheriff Lombardo said.