Stephen Paddock's girlfriend Marilou Danley said her partner was a "kind, caring, quiet man" in a statement released through her lawyer after she was questioned by FBI investigators trying to understand the Las Vegas shooter's motive.

Paddock, 64, killed 59 people and injured hundreds more when he unleashed a storm of bullets from his hotel room on the 32nd floor of the Mandalay Bay on a crowd enjoying a the Route 91 Harvest country music festival nearby. It is the deadliest mass shooting in modern US history.

The gunman died from a self-inflicted gunshot wound as police stormed his hotel room. In the room, his car, and at two of his properties in Nevada, police found a huge arsenal of weapons, including modified rifles - so they could shoot more bullets faster - and explosives. But Paddock left no obvious signs of a motive and authorities remain puzzled about why he did it.

Danley, 62, who lived with Paddock at their home in Mesquite, around 80 miles northeast of Las Vegas, became a person of interest to investigators. She was out of the country visiting family in the Philippines, but quickly returned to the US for questioning by the FBI. She is not a suspect.

In her statement, Danley, who Paddock wired $100,000 in the days before his attack, said she is "devastated by the deaths and injuries".

"I knew Stephen Paddock as a kind, caring, quiet man," Danley said. "I loved him and hoped for a quiet future together with him. 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.

"A little more than two weeks ago, Stephen told me he found a cheap ticket for me to the Philippines and that he wanted me to take a trip home to see my family. Like all Filipinos abroad, I was excited to go home and see family and friends. While there, he wired me money, which he said was for me to buy a house for me and my family.

"I was grateful, but honestly, I was worried that first, the unexpected trip home, and then the money, was a way of breaking up with me. It never occurred to me in any way whatsoever that he was planning violence against anyone.

"I have not made a statement until now because I have been cooperating with the authorities, and I voluntarily flew back to America, because I know that the FBI and Las Vegas police department wanted to talk to me, and I wanted to talk to them.

"I will cooperate fully with their investigation. Anything I can do to help ease suffering and help in any way, I will do. Please respect my privacy and my family's privacy."

Marilou Danley Las Vegas suspect
Police in Las Vegas are looking for Marilou Danley in connection with the mass shooting that left 20 people dead. Facebook