Paddock's girlfriend, Marilou Danley, 62, who was in the Philippines at the time of the Sunday night shooting, was met by Federal Bureau of Investigation agents at the Los Angeles airport late Tuesday, according to a law enforcement official who wasn't authorized to discuss the matter publicly and spoke to The Associated Press on condition of anonymity.
Meanwhile, police released new body cam video showing the chaotic and confusing moments when officers arrived on the scene of Sunday's deadly mass shooting. NBC says that Danley traveled to the Philippines on September 25 via Hong Kong.
"We are making arrangements to contact her upon her return", he said. Paddock ended the rampage by killing himself.
Clark County Sheriff Joseph Lombardo told reporters meeting President Trump's plane in Nevada that the interview was to be conducted shortly.
Workers at Stephen Paddock's local Starbucks immediately remembered the tall man with a big beer belly and bags under his eyes who used to come in with his girlfriend, according to the Los Angeles Times.
"The fact that he had the type of weaponry and amount of weaponry in that room, it was preplanned extensively", the sheriff said, "and I'm pretty sure he evaluated everything that he did and his actions, which is troublesome". The 64-year-old, retired, twice-divorced accountant - who at one time had jobs at the US Post Office and the IRS, a representative of the Office of Personnel Management told CNN - had no significant criminal history and was previously unknown to police.
At this point, Paddock's motive and aims remain a mystery to investigators.
He used "bump stocks", attachments that allow a semi-automatic rifle to mimic a fully automatic weapon by unleashing an entire large magazine in seconds.
The gunman reportedly wired $US100,000 to The Philippines the week before the shooting.
The former Gold Coast woman, 62, had been living with Paddock in Mesquite, Nevada, before the shooting but was in the Philippines when the massacre occurred.
"We haven't absolutely ruled out anything in this investigation", said Mr McMahill, when asked about a potential Philippines terrorism link.
Law enforcement officials who confirmed the wire transfer to NBC did not reveal who the bank account belongs to.
Her sisters in Australia have since told 7 News they believed he "sent her away" to the Philippines prior to the shooting.
But Eric Paddock said his brother had led an otherwise normal life. Stanton said Lombard is expected to put out a statement later Wednesday.
A raid on the home they shared discovered 23 additional firearms, explosives and thousands of rounds of ammunition.
Authorities also found thousands of rounds of ammunition in Paddock's Mesquite home, and an ingredient used in explosives was discovered inside the killer's auto.