There was no evidence at this point to indicate that the mass shooting in Las Vegas this week was terrorism, a Federal Bureau of Investigation agent told a news conference on Wednesday.
In response to a question, Clark County Sheriff Joseph Lombardo said investigators were examining the possibility 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.
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 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 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 the FBI was questioning her.
A Federal Bureau of Investigation official in Las Vegas, meanwhile, said no one has been taken into custody.
But 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. Lombardo 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.
Nearly 500 people were also injured when Paddock, 64, 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, bringing the total death toll to 59.
Police recovered nearly 50 firearms from three locations they searched, nearly half of them from the hotel suite. Twelve of the rifles there were fitted with so-called bump stocks, officials said, allowing the guns to be fired almost as though they were automatic weapons.
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