The authorities investigating the Las Vegas shooting have turned to the shooter's girlfriend, Marilou Danley, hoping to get clues about the gunman Stephen Paddock's motives and what may have sparked the deadliest mass shooting in modern US history.

Marilou Danley returned to the United States on Tuesday night from the Philippines.

She was accompanied by the Federal Bureau of Investigation in Los Angeles, where the Las Vegas Police planned to question her, CNN quoted law enforcement source, as saying.

The FBI agents will pose two critical questions to Danley: Did she have any idea about what motivated him, and did she have any knowledge of what was about to take place and not alert authorities?

The 64-year-old Stephen Paddock was holed up in a high-rise hotel overlooking the Las Vegas Strip and opened fire on concertgoers at a country music festival in which 59 people were killed and more than 500 others injured.

The police believe Paddock acted alone.He had an arsenal of weapons, including bump-fire stocks found in the hotel, which is a legal device that enables a shooter to fire bullets rapidly, similar to an automatic rifle.

Paddock had outfitted 12 of his firearms with the bump stocks, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Las Vegas shooter Stephen Paddock encouraged his live-in girlfriend, Marilou Danley, to leave the country before the attack.

"I know that she doesn'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,"  CNN quoted one of Danley's sisters, as saying.Stephen Paddock, the Nevada man who authorities identified as the gunman who killed 59 people on Sunday night, 'continued to fire at a progressive successive rate for approximately nine minutes' after authorities received a 911 call, Clark County Sheriff Joseph Lombardo said.  -- ANI