LAS VEGAS (REUTERS) - The girlfriend of the Las Vegas gunman who killed 58 people and himself in the deadliest mass shooting in modern US history was questioned by the FBI on Wednesday (Oct 4) and said she had no idea he was "planning violence against anyone."

Marilou Danley, who returned late on Tuesday from a family visit to the Philippines and is regarded by investigators as a "person of interest," said through a lawyer that the carnage Stephen Paddock, 64, unleashed while she was abroad caught her completely unaware.

"He never said anything to me or took any action that I was aware of that I understood in any way to be a warning that something horrible like this was going to happen," Danley, 62, said in a written statement read to reporters by her attorney in Los Angeles, where she was being questioned.

"I knew Stephen Paddock as a kind, caring, quiet man. I loved him and hoped for a quiet future together with him," she said. "It never occurred to me in any way whatsoever that he was planning violence against anyone."

Danley, an Australian citizen of Filipino heritage, said she flew back to the United States voluntarily "because I know that the FBI and Las Vegas Police Department wanted to talk to me, and I wanted to talk to them."

A FBI official in Las Vegas, meanwhile, said no one has been taken into custody.

But Clark County Sheriff Joseph Lombardo told reporters he found it hard to believe that the arsenal of weapons, ammunition and explosives recovered by police in their investigation could have been assembled by Paddock completely on his own.

"You have to make an assumption that he had some help at some point," Lombardo said at a news briefing. He said the attack was the obvious outcome of meticulous planning.

"What we know is that Stephen Paddock is a man who spent decades acquiring weapons and ammo and living a secret life, much of which will never be fully understood," the sheriff said.

In response to a question, Lombardo said investigators were examining the possibility that Paddock's purchase of more than 30 guns in October 2016 may have been precipitated by some triggering event in his life. He did not elaborate.

If Paddock did have any accomplice, there remained no evidence as yet "to indicate terrorism" in the shooting spree, said Aaron Rouse, FBI special agent in charge of the Las Vegas field office.

Fifty-eight people died and 489 injured when Paddock strafed an outdoor concert with gunfire on Sunday night from his 32nd-floor suite of the Mandalay Bay hotel on the Las Vegas Strip.

He took his own life before police stormed his room, where they found as many as 23 guns, bringing the total death toll to 59.

Twelve of his rifles were fitted with so-called bump stocks, officials said, allowing the guns to be fired almost as though they were automatic weapons.

US President Donald Trump visited Las Vegas on Wednesday, marking the first time since taking office that he has had to confront a major mass shooting.

FOLLOWING THE MONEY

Investigators, at a loss to determine a motive for Sunday's bloodshed, have focused on Danley, who had shared Paddock's retirement community condo in Mesquite, Nevada, north-east of Las Vegas, before leaving the United States for the Philippines in mid-September.

Federal Bureau of Investigation agents met her plane at Los Angeles International Airport and took her away for questioning, two US officials briefed on the case told Reuters.

The officials said that as of midday Wednesday, there was no indication she was aware of Paddock's plans.

Investigators questioned her about Paddock's weapons purchases, a US$100,000 (S$136,055) wire transfer to a Philippine bank that appeared to be intended for her, and whether she saw any changes in his behaviour before she left the United States.

"Assuming she had no role in his actions, the most important thing is any light she can shed on Paddock's motive," said one official, who spoke about the investigation on condition of anonymity.

Danley said in her statement that Paddock had bought her an airline ticket to visit her family and wired her money to purchase property there, leading her to worry that he might be planning to break up with her.

Paddock's brother Eric told reporters the US$100,000 transfer was evidence that "Steve took care of the people he loved," and that he likely wanted to protect Danley by sending her overseas before the attack.

She arrived in Manila on Sept 15, flew to Hong Kong on Sept 22, returned to Manila on Sept 25 and was there until she flew to Los Angeles on Tuesday night, according to a Philippine immigration official.

Discerning Paddock's motive has proven especially baffling given the absence of the usual indicators that have emerged in other mass shootings. He had no criminal record, no known history of mental illness and no outward signs of social disaffection, political discontent or extremist ideology, police said.

A US official familiar with the investigation said there was no evidence that Paddock had contacts with any extremist groups, or that he might have sought out militant groups online that could have incited him to carry out a mass shooting.

Trump, touring a hospital in Las Vegas, told reporters Paddock was "very demented."

Meeting with officers who rushed toward the shooter, Trump asked the head of the Las Vegas Metropolitan Police Department if investigators were any closer to establishing a motive.

"We've had a couple good leads and we're working our way through it," Sheriff Joseph Lombardo told the president.