The Las Vegas shooter was so hooked on gambling he played up to 1,000 hands of video poker in a single hour - at a cost of $100,000.
Stephen Paddock bet the colossal sums by playing $125 a time hands at 'ferocious' speeds for eight hour stints in casinos on The Strip and in Reno.
Top video poker players told DailyMail.com that players like Paddock look like 'stenographers' on the machines because their fingers move so fast.
They had seen Paddock at exclusive VIP tournaments in Las Vegas where he won and lost six-figure sums.
The players described him was a 'low level high roller' but he still would have got perks like free limousine rides and $10,000 of free money to play with.
Drinking concern: Gamblers say they saw Stephen Paddock playing video poker with a 'constant stream of booze' by his side when he was a guest at VIP tournaments
Fast and furious: These are the video poker machines which allowed Paddock to gamble stakes of up to $100,000 in an hour by playing multiple hands at once
Crack cocaine: A review in the late 1990s compared the machines to the most addictive drugs but they also offer some of the best odds of coming out even, experts say
Paddock's girlfriend Marilou Danley was taken on all-expenses paid shopping trips and they would have stayed in expensive hotel suites for free.
DailyMail.com can also disclose that other high rollers were concerned about Paddock drinking a 'constant stream of booze' whilst he was playing.
They described him as a 'heavy, heavy drinker' and wondered if his high alcohol intake contributed to his mental deterioration.
Paddock shot dead 58 people and injured more than 500 on Sunday when he opened fire on a music festival from his suite on the 32nd floor of the Mandalay Bay casino before shooting himself dead.
The FBI are no closer to understanding the motive of a man who his brother Eric described as 'just a guy'.
But what is clear is that the 64-year-old had a passion for gambling which he indulged in his retirement with the estimated $2 million fortune he had built up through a real estate business.
Friends have said that Paddock, a former accountant and auditor, developed what he thought was an algorithm which would let him beat the system at video poker.
Anthony Curtis, a former professional gambler and currently the owner and publisher of Las Vegas Advisor, a website covering the casino business, told DailyMail.com that Paddock was not a 'whale' in the casino world, meaning the very biggest spenders.
But he was a known quantity and would be seen at invite-only tournaments where players would compete for $50,000 cash prizes.
Curtis said that according to players in Vegas he knows, Paddock 'gambled big, he really did', but he was not sociable.
He said: 'Nobody knew him, that was the weirdest thing
'People I know only knew of him, they didn't know him. He wasn't friendly but wasn't unfriendly.'
If anything stood out it was Paddock's drinking, said Curtis, who is a consultant for the Alea Consulting Group, which represents gambling experts.
He said: 'He was a heavy drinker, heavy drinker, that's what I heard... some people thought he was a pure alcoholic. He had a constant stream of booze coming his way'.
Curtis said that video poker players he knew told him that Paddock played $25 a hand machines where you can put in five bets at one time, bringing the stake for each game up to $125.
Players at his level would be playing at 800 to 1,000 hands an hour, or one every 3.6 seconds - Curtis said he and his former playing friends used to time each other to see who was fastest.
Players have to go quickly to improve their likelihood of getting hands like a royal flush which come on average every 40,000 hands and might earn $50,000 on a $125 wager.
Red carpet welcome: As a VIP gambler, Paddock was given a warm welcome with 'comps' which included room and board. Even bigger gamblers get private jets but Paddock was not a 'whale'
Also benefited: VIP poker invitations come with free shopping sprees for partners as well as meals and hotel rooms 'comped'
In a game of video poker the player is up against just the machine and not a human dealer and each hand is dealt from a new 52-card virtual deck.
By working out the probabilities of hands players, can beat the house and at the Mandalay Bay video poker machines pay out a maximum of 99.17 percent, or $99.17 for every $100 wagered.
By the time you add in the perks, or 'comps', short for complimentary, they are more than breaking even.
For the highest rollers, they are treated like rock stars and essentially get anything they want, be it front row tickets to a concert, Super Bowl tickets and a Lear Jet to take them wherever they want.
Even at the lowest level of such tournaments they will get 'full RFB', meaning room, food and board. The presence of the amblers helps build the casino's image.
Michael Shackleford, a former professional actuary and video poker player who now has a career analyzing casino games, said: 'The low level players will get free low end meals, buffets, maybe free rooms midweek
'As you get up they've going to treat you to the better restaurants, better rooms, free tournaments, free airfare, free transportation.
'The way the casinos look at it is every player has a particular value.
'If you have a player who is losing $1m a trip, the casino will give him $300,000 worth of stuff just for coming in.
'They don't like to give you money, they prefer to do it in the form of comps. In Vegas it's fiercely competitive for the big players, they often negotiate to get the best offer.'
Shackleford said that video poker players tended to be smart, disciplined and patient.
He said that you have to be able to sit down at the machine and play it for hours at speed but if you press one button wrong it could cost you two hours in value to play.
He said: 'It's a very volatile game and if you're going to be playing it professionally.
'You go up and down like a roller coaster. You need nerves of steel to keep playing in the bad times.'
Shackleford himself used to lose $25,000 in a single day - but once won $40,000 when he got a royal flush.
Expert: Bob Dancer made $1 million from video poker but warns: 'There are a lot lot lot lot more net losers than there are net winners.'
He said: 'In the long run I can say it's averaged out and my results are where they should be.
'You just say you have to believe in the math, it doesn't matter if you win or lose, it matters if you had a good bet and treat it like a job'.
Shackleford's assessment of Paddock echoed that of the other experts; he was not a professional but had clearly studied how to win and had some ability.
He said: 'I think he was a smart recreational gambler who saw it as a way to have a free vacation. That's my impression of the guy.'
Curtis said: 'Think about this; if you want to go to an NFL game you have to pay for a personal seat. It can cost tens of thousands of dollars just to see your team play.
'What's the difference between that and what he was doing? He was paying for entertainment - that's how I see the whole thing.'
Video poker was described by the National Gambling Impact Study Commission in the late 1990s as being the 'crack-cocaine' of gambling because it is so addictive.
Reports have said that those who are most addicted have brain disorders similar to drug addicts.
Among the infamous cases of video poker players is San Diego's former mayor Maureen O'Connor.
She took $2 million from the foundation set up for her dead husband, bet a cumulative total of more than $1 billion at casinos on a wild spree of wins and losses - and ended up owing $13 million.
Players are drawn to the game because of odds which are better than most other casino games.
John Grochowski, a longtime gambling columnist and author, said that the average person can get the a handle of playing video poker in a month using books and programs that are widely available.
But he doubted that it was possible to win consistently at a high level and said that Paddock would have been 'deluded' if he thought he had a system that would beat the house.
He said: 'You need either to be in a position where the money just doesn't matter and you want the thrill to gamble.
'If you're really trying to make money at this and you're fooling yourself into thinking you can make money at this you need to think you're smarter than you really are.
'You have to go in absolute convinced your system works and stick with it in the bad times and roll with the losses and unfortunately most people can't really roll with losses at that level.
'Discipline is the key. You need to stay within your own bankroll, don't bet money you can't afford to lose.
'For some people video poker is the crack cocaine of gambling, it's certainly engaging, it's interactive and it will hold your attention.
'For a certain personality that may be true but there also may be personalities who are going to stay within their limits and stay within what they can afford'.
Few have been more successful at video poker than Bob Dancer, an expert and author of 10 books on the subject.
Dancer has made more than a million dollars playing video poker for 20 years using strategies he developed himself.
The bulk of his winnings was in the late 1990s and early 2000s including one 12-month stretch where he and his ex-wife Shirley would go on a $100,000 losing streak - then make $70,000 back.
In February 2001 at the MGM Grand in Vegas he made $100,000 on a royal flush within 15 minutes of playing and less than half an hour later Shirley won $400,000 with the same hand on a different machine.
Dancer said that it was possible to make a living being a professional video poker player. He said that the key factor was who had the advantage; him or the casino.
Back in the 1990s the describes the casinos as 'mathematically challenged' and he was able to work out his winnings faster than they could, giving him the advantage.
He describes the feeling after winning a big payout as being 'bulletproof' and that 'you think it's because you're smart'.
When faced with a big loss he shrugged it off because he was sure that over time it would even out, but Shirley found it harder.
Dancer said: 'Shirley was scared of the swings and every time we lost she would get all tense up and we had a masseuse on retainer for her.
'We'd lose $30,000 in a night and she'd think that was an automobile and it would be extremely traumatic than her.
'She could deal with the wins but the losses - I shrugged them off - she took them really personal and really hard.'
As for Paddock, Dancer said: 'I never met Mr Paddock. I never heard his name before he was dead.
'I do not know if he was a successful player or not.
'It's clear he hit some jackpots at some times. Whether he was a net winner or a net loser I have no idea.'
He added: 'There are a lot, lot, lot, lot more net losers than there are net winners.'