She was taken out a back way so she wouldn't be seen in public, and she was met by Federal Bureau of Investigation agents immediately upon landing, multiple law enforcement sources told ABC News.
News that Paddock was the man responsible for killing 59 people and wounding more than 500 was shocking to Alarcon. Paddock killed himself in the 32nd floor hotel room he used as a vantage point to rain bullets down on people attending the Route 91 Harvest festival.
Investigators said that Marilou Danley, Geary Danley's ex-wife and a person of interest, was a companion of Stephen Paddock.
"It happened a lot", Esperanza Mendoza, the supervisor of the Starbucks inside the Virgin River Casino in Mesquite, Nevada, told the Los Angeles Times.
The first call reporting shots fired came at 10:08 p.m. Sunday, and the gunfire didn't stop until 10:19 p.m., Clark County Undersheriff Kevin McMahill said.
Police say Paddock set up surveillance cameras in the hallway outside of his hotel room. "And you thought you know the person yourself", one of Danley's sisters said.
According to her sisters, Danley is now the only person who can shed light on the possible motives and mindset of the gunman despite being unaware of his impending actions, defending her as a "good person".
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The Las Vegas shooter's girlfriend has voluntarily returned to the U.S. from the Philippines as authorities probe for any possible links to the case.
As authorities began investigating the mass shooting in Las Vegas on Sunday night, Marilou Danley quickly became someone they wanted to talk to.
Ms Danley has returned to the USA, where she has been based for the past two decades, following a brief trip to the Philippines, where she was reportedly born. 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.
"Our family doesn't know Stephen Paddock, and has no knowledge of Marilou's relationship with Mr. Paddock".
Las Vegas Sheriff Joe Lombardo on Wednesday said he expected a "substantial amount" of information on Paddock's motive would emerge in the next 48 hours.
Danley's boyfriend Stephen Paddock was the gunman.
Chris Sullivan, the owner of Mesquite's Guns & Guitars shop, issued a statement confirming that Paddock was a customer who cleared background checks and said his business was cooperating with investigators.
He said the family did not plan to hold a funeral for his brother, who was not religious, saying it could attract unwanted attention.