Las Vegas shooter Stephen Paddock was part of an elite club of high-roller gamblers whom casinos lavished with free hotel rooms, top-shelf food and alcohol, sporting tickets, invites to VIP parties and shopping sprees.
Paddock was known in high roller circles as a "loner" who "drank a lot", according to Anthony Curtis, a former professional gambler who now runs Las Vegas Advisor, a site that offers tips to visitors.
Curtis's contacts say Paddock would sink as much as $1000 an hour and $100,000 a day into video poker machines like "it was a breeze" and was a regular presence at the Cosmopolitan, Wynn and Mandalay Bay casinos on the Las Vegas Strip.
He was also known to collect tens of thousands in the one sitting, reports News.com.au.
"This puts him in the realm of a high roller, for sure," Curtis told news.com.au.
In casino parlance, he was known as a "low seven" or a "low-level high roller", but even those on that scale are treated to excessive perks.
Paddock was a "full RFB", which means his room, food and beverage were all paid for by the casinos to keep him happy and gambling.
"That means he's running the place. He's in the best hands," Curtis said.
"We're talking a limo to the show of his choice, his girlfriend would get a $5000 shopping spree, he would have been invited to all of the high roller parties.
"He was playing at that level."
Paddock was staying for free at the Mandalay Bay hotel when he shot dead 58 people and injured nearly 500 more from the 32nd floor, and he was seen playing video poker there three days before the attack, The New York Times reports.
The freebies offered to him would have also extended to tickets to major sporting events, such as the Super Bowl or the Conor McGregor-Floyd Mayweather fight, and he would have been sponsored to play in tournaments with $100,000 prizes up for grabs, Curtis said.
But while he was a fixture at the casinos, he tended not to socialise.
"When his name was released, it didn't register with anybody, but when his picture circulated, everybody said 'I know that guy'," Curtis said.
"He kept to himself. He drank a lot. Even in the picture he looks half loaded.
"Nobody knew him personally; he was a loner [but] he was running in a pretty well-heeled crowd.
"The fact that he kept to himself is not surprising at that level. People at that level tend to be quiet."
Paddock favoured video machines at the Mandalay Bay casino because they returned a high rate - 99 per cent. He made up any losses by taking advantage of the all the free incentives, or comps.
"The street name for it is 'comp hustling'," Curtis said.
An Australian man who knew Paddock told The Guardian that he took a mathematical approach to gambling, playing the algorithms to make huge payouts. He made an annual income "well over a senior executive's wage" through gambling alone.
"And how he obtained that: the algorithms behind his methodology of gambling - only on machines, not on tables," said the Brisbane man, who declined to be named.
"He was extremely intelligent, methodical, conservative - guarded - and strategic. A planning, thinking type of guy."
Eric Paddock told reporters this week that his brother treated gambling like a full-time job.
"He gambled for 20-plus years successfully," he said. "It's like a job to him. He did it mathematically; he did it because it was a way to have a fun life.
"He was an independently wealthy, no-ties-attached guy.
"If he wanted to get on a plane to Japan and have sushi tomorrow, he did that. Now, he'd probably have the casino pay for it by saying he'd go to a casino there, or something."
Eric said he and his brother once enjoyed thousands of dollars worth of sushi on a casino's dime. Paddock just had to pay the tip.
"He has the highest level of membership at these hotels," he said.
But while he was a valued customer, he was also known for creeping out the other high rollers.
"He loved to stare at other people playing," John Weinreich, a former executive host at the Atlantis Casino in Reno, Nevada, told the Times. "It was not a good thing because it would make other VIPs in the high-limit area uncomfortable.
"One of my guests once said to me, 'He really gives me the creeps'."
Based on Paddock's reputation, Curtis does not believe that his gambling habit had anything to do with why he turned those guns on the music festival crowd on Sunday.
"The media tried to make the case that it was causal, that he probably lost money and went berserk. That's as far from the truth as can be," Curtis told news.com.au.
"I mean if he was into stamp collecting, would you say that the stamps made him do it?
"It wasn't the gambling that made him do it."