The sister of the Filipina-Australian girlfriend of Las Vegas mass-killer Stephen Paddock says she was sent to the Philippines two weeks before the massacre so she couldn't interfere with his plans.
Marilou Danley has arrived back in the US to face questions about the massacre and the reported $US100,000 her boyfriend transferred to her in the Philippines before he killed 58 people and injured more than 500 as he fired from a 32nd floor casino hotel suite on Sunday night.
Ms Danley was taken through Los Angeles International Airport by FBI agents in a wheelchair on Tuesday night after flying in from the Philippines.
The 62-year-old former Queensland resident, who left Australia in 1989 and lived with Paddock in Nevada, will be escorted to Las Vegas.
"We have a lot of questions," Las Vegas Undersheriff Kevin McMahill told reporters.
Her sister who lives in Queensland says she is a good person and knew nothing about Paddock's plot to slaughter dozens of revellers at a country music festival on the Vegas Strip.
"I know that she don't know anything as well like us. She was sent away. She was away so that she will be not there to interfere with what he's planning," her sister, whose name was not revealed, told the Seven Network.
"She didn't even know that she was going to the Philippines until Steve said 'Marilou I found you a cheap ticket to the Philippines'.
"He sent her away so that he can plan what he is planning without interruptions. In that sense, I thank him for sparing my sister's life. But that won't be to compensate the 59 peoples' lives.
"No one can put the puzzles together. No one except Marilou. Because Steve is not here to talk anymore, only Marilou can maybe help.
"She probably was even more shocked than us because she is more closer to him than us. To be able to find out the person you love, and live with, can do such a thing and you thought you knew the person yourself.
"Marilou Danley is my sister, she is a good person and gentle soul. A mother, a grandmother, a sister, a friend.
"He done this solely himself.
"Marilou seemed madly in love with Steve.
"Maybe if Marilou was there this maybe didn't happen because she won't let it happen. She would definitely stop whatever he was planning."
Las Vegas Sheriff Joseph Lombardo says Ms Danley is "a person of interest" and hopes she will provide a "substantial amount" of information on Paddock's motives.
Paddock, 64, who used a sledgehammer to smash holes in two thick glass windows of his Mandalay Bay hotel suite, used high-powered rifles modified to be automatic for the mass shooting.
Forty-seven firearms were found in three locations - Paddock's hotel suite, the home he shared with Ms Danley 130km away in Mesquite and another property in Reno, Nevada.
Ms Danley was born in the Philippines and moved to Queensland in the early 1980s before moving 28 years ago to the US where she worked in casinos.
Authorities initially distanced Paddock's murderous rampage from terrorism, but with the lack of a motive, Ms Danley's presence in the Philippines and the money transfer, they refused to rule it out.
"We haven't absolutely ruled out anything in this investigation," said Undersheriff McMahill, when asked about a potential Philippines terrorism link.