A Las Vegas prostitute has claimed that 64-year-old Stephen Paddock, the gunman responsible for one of the worst mass shootings in America's history, liked to act out violent rape fantasies and previously paid her $6,000 a time for a series of aggressive sexual encounters.

The 27-year-old escort told The Sun on Sunday that she was hired by Paddock several times between November 2015 and June 2016 and claimed that they previously stayed at the Mandalay Bay hotel, a location which played a key role in the atrocity earlier this month.

"When I first met Stephen I had left an abusive relationship and was starting all over again with nothing," the escort said, adding that he was a "paranoid" man who liked to talk about conspiracy theories involving the US government.

"He seemed like he wanted to help," she continued. "We would go to the casinos together and he would spend hours drinking and gambling.

"But when he would have a winning streak, we would go back and have really aggressive and violent sex."

Texts sent between the pair where he boasted of being "born bad" reportedly showed Paddock asking to tie up the girl as she screamed for help.

The escort, who was not named in the newspaper's report, said that she didn't see Paddock again after starting a new relationship last year.

Investigators are yet to determine a motive for the 1 October attack which left 58 people dead and more than 500 injured. The shooter holed himself up on 32nd floor of the hotel in the heart of Las Vegas and opened fire on a 23,000-strong crowd attending a music concert below.

Police believe that he used "bump stock" devices on a variety of semi-automatic machine guns in order to increase their rate of fire. Clark County Sheriff Joe Lombardo told local media after the attack that evidence suggested the incident was "pre-planned extensively."

Paddock was found dead in his hotel room with a self-inflicted gunshot. Investigators believe he acted alone but have appealed for more information from the public - including call girls.

"He had a dark and twisted side," the Vegas escort told The Sun on Sunday. "But even so, I could never have imagined he would do something like this."

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US Air Force One, with President Donald Trump aboard, departs Las Vegas past broken windows at the Mandalay Bay hotel, from where Stephen Paddock conducted his mass shooting Mike Blake/Reuters