Video has emerged of the Las Vegas mass shooter tripping and falling at a Sin City casino in 2011. The fall set off a $100,000 lawsuit that left the shooter in debt until the day of the attack.

Security footage caught Stephen Paddock, the man named by police as the shooter, falling to the ground while walking through Las Vegas’s Cosmopolitan Hotel in 2011. The frequent gambler claimed he slipped on a puddle of liquid, and attempted to sue the hotel for his medical bills and pain and suffering, according to NBC News.

An attorney for the hotel, Marty Kravitz, told NBC that Paddock appeared “dishevelled” and “bizarre” when he arrived for his deposition, but added: "This is not a guy that I would have looked at and thought, 'He's going to commit a crime one day’.”

Las Vegas shooting: Who is gunman Stephen Paddock?

Paddock’s case against the hotel went to arbitration in 2014. The arbitrator ruled in favour of the Cosmopolitan and dismissed Paddock’s claims of negligence as “without merit”. At the time of the shooting, Paddock still owed $270 in court fees, according to NBC.

The case plays into an increasingly confusing picture of the man who opened fire on a crowded concert on Sunday, injuring more than 500 and killing at least 59. The shooting was the deadliest in US history.

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According to records and family members, Paddock was a retired accountant who had been divorced twice and lived with his girlfriend in Mesquite, Nevada. His brother, Eric Paddock, said the 64-year-old had made millions in real estate, and enjoyed high-stakes gambling in his retirement.

“He was a gambler, that was his job,” Mr Paddock told reporters. “He was a wealthy guy, playing video poker, who went cruising all the time and lived in a hotel room.”

Paddock was given a “Seven Stars” status at Caesar’s Entertainment casinos – an invitation-only designation for high-rollers, sources familiar with the shooting investigation told NBC News. Sources told the outlet that Paddock had gambled more than $10,000 a day in the days leading up to the attack.

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Around that same time, authorities say, Paddock rented a large suite at the Mandalay Bay Resort and Casino and started stockpiling more than 20 weapons. On 1 October, he broke through the hotel room windows and fired on a crowd of concert-goers outside.

A SWAT team eventually broke into the hotel room to stop him, but had Paddock killed himself before officers could reach him. Officials are still hoping to interview his girlfriend when she returns to the country.