LAS VEGAS — Stephen Paddock wanted to win and, like any savvy video poker player, knew which machine to lock down at Mandalay Bay.

There was only one in the casino — a Jacks-or-better 9-6 machine, meaning it paid 9-to-1 credits on the full house and 6-1 on the flush and only offered the casino slim advantage. Mandalay Bay was having a contest for a $100,000 drawing and players, based on the amount of their play the next day, would get tickets to enter.

He got ready to work.

David Walton, a video poker playing pro, headed down to the casino floor early to nab the good machine.

There sat Paddock. Not playing it. Just sitting there. Waiting.

Walton settled into the machine next to him — not one with as generous a payout schedule — and waited for midnight. When it struck, Paddock hit the machine lightning quick, going at a rate of $120,000 per hour. He barely spoke.

Walton said Paddock played 24 hours straight that day in 2007. Before the drawing, Walton wandered over to look at the 4-foot-by-4-foot drum holding all the tickets to the drawing to size up his chances at the $100,000.

Those hopes were diminishing quickly.

"Every ticket on there I saw through the mesh said 'Stephen Paddock. Stephen Paddock. Stephen Paddock,' " Walton said.

"He won."

A decade later, Paddock, 64, would ride the elevator up to the 32nd floor of the Mandalay Bay, smash out two windows in his suite with a hammer, and aim a 10-minute, rapid-fire volley of gunfire at the 22,000 people gathered below for a country music festival. He hit hundreds, and killed 58.

Paddock, his brother Eric Paddock told reporters last week, gambled for more than 20 years. "Successfully ... . He did it because it was a way to have a fun life, and he didn't go poor doing it."

Most Americans are familiar with poker, from small-stakes home games to final-table showdowns at the World Series of Poker, a game in which reading your opponent can be as important as the cards that are dealt. The game Paddock played is different. Computers don't bluff. They don't distract, they don't order too much gin and make mistakes. They deal in numbers.

For years, Paddock and other professionals had figured out how to make the machines pay, tipping their advantage by a few hundredths of a percentage point by identifying the right games and maximizing points while playing.

Paddock was comfortable with calculation.

"He was a math guy," Eric Paddock said. "He could tell you off the top of his head what the odds were down to a tenth of a percent on whatever machine he was playing. He studied it like it was a Ph.D. thing. It was not silly gambling. It was work."

For the most part, it was lonely work.

"The video poker machines that Paddock played often attract locals who are not seeking the excitement and rowdiness of live poker games," said Scott Roeben, who runs the Vital Vegas blog. "It is not glamorous, it's not exciting. It's a game of just slogging away. It's methodical and solitary."

For Paddock, who was also a multimillion-dollar real estate investor, it was at least a steady income over a period of years.

"He's got the highest level of membership card at a lot of these hotels. If a lot of these hotels say they don't know Steve, they're lying," Eric Paddock said.

But his brother also "didn't love the casino," Paddock said. "The casino was a means to an end. The casino to him was like a job in Toyota in Japan, where you live in the Toyota apartments across the street, and then you go to the Toyota factory to work. That's what the casino was. It's a place where you lived and they were nice to you, and you could get it paid for by playing slots."

But those familiar with the world of video poker say winning has become much harder as casinos, mostly on the Las Vegas Strip, have added machines that hold a better house advantage.

Sometime a little more than a decade ago, the odds changed. And not in Paddock's favor.

Video poker began in the 1970s when William Redd — known as the "King of Video Poker" — married video game technology with gambling. In 1980, he founded International Game Technology and it went public the following year.

It took off.

In Redd's 2003 obituary in the Los Angeles Times, Bill Thompson, a Las Vegas psychologist, called video poker "the crack cocaine of gambling."

The machines, he said, became foundational for the casinos.

"Video poker machines made amateur players think they were playing a casino game rather than just pulling a handle," he said. "The downside is the machine hooked a lot of people."

It was this quality that prompted Walton to quit several years ago.

"Video poker is the worst of the worst. The reason it works so well is it compels you to keep playing through random reinforcement," he said. "The next hand might be the big one. You might get a flush or a full house, and that keeps you hanging in there. It gives you just enough positive feedback to keep you hooked into it."

The elimination of most machines that don't have a broad, built-in house edge has narrowed the field of those who are ready to drop millions, said Jean Scott, who has written several books about video poker and has played at a professional level for decades.

"The advantage plays have gone away in recent years. It is getting hard to win," Scott said. "The casino bean counters are getting tougher."

Walton said he saw Paddock make some mistakes. He gave him poor advice on a hand once while the two were gambling next to each other at the Wynn Casino. Overall, he said, Paddock was a solid player "with some leaks" in his game.

Paddock, say some of those who watched him play, seemed to be in it not to get rich so much as to enjoy the perks that go along with being a regular.

Anthony Curtis, a professional gambler who runs one of the authoritative guides to the Las Vegas casinos, the Las Vegas Advisor, said Paddock was what is known as a "comp hustler" — someone who plays well enough to get significant compensation in the form of suites, limos and food.

"These kind of players play for the complimentary services ... this guy was not social, but he liked to see himself, his girlfriend and anyone else he brought along be treated well," Curtis said. "He was a relatively knowledgeable video poker player and definitely knew what he was doing. A player like him does not really lose money — they play within their means to an actual plan."

The means with which to play at those levels might have been buoyed by $5 million in gambling income reported on his 2015 taxes, according to a report obtained by NBC last week.

But gambling experts also were quick to point out the $5 million doesn't say how much of that could've been lost as quickly as it was won.

Scott said some people will chat and play while sitting with their friends, but those who are playing to win tend to focus because any slip-up can be costly.

Paddock's style seemed to be focused, she said. She considered him a "hefty" bettor — though not a "whale," a term used by casinos for a small group of players who drop millions during the course of a weekend.

From most accounts, Paddock was a study in intensity; he didn't talk much once he hit the casino floor.

But drinking seemed to be a common denominator among those who saw him in action.

"He was a heavy drinker and that is what impressed upon ... them," Curtis said.

Paddock had lived in the town of Mesquite, Nev., 80 miles north of Las Vegas, since purchasing a home for cash in an upscale retirement community on a golf course with his girlfriend. He was known at the casinos there, and there, too, some described him as a drinker.

Kallie Beig, who worked at the local Great Clips, told CNN she had cut his hair at least three times during the past three years. He smelled strongly of liquor each time.

It was the all-night gambling, she said.

He frequented Peggy Sue's, a popular bar in town, residents said. The bartenders and regulars said he was seldom without a drink. A neighbor said her husband saw Paddock at the bar frequently, and others said he and his girlfriend, Marilou Danley, were regulars at Friday night karaoke at Peggy Sue's — although it was Danley who liked to sing.

She favored older, slower songs, one regular at the bar remembered. Maybe Patsy Cline.

Roeben, who runs the Vital Vegas blog, said most serious players never mix poker and alcohol: Even being tired can cause a player to slip and hit draw instead of hold. Repeated mistakes during the course of an hour are financially fatal given the tougher machines.

"Accuracy is more important now than ever," Scott said. "Just a few slips can cost you quite a lot."

The high-end slot areas in Mandalay Bay that made up Paddock's gambling world — along with several similar areas along the Strip — tend to be quieter. Cocktail waitresses are attentive, moving with efficiency in heels and revealing light-blue outfits between the walled-off area and the bar.

Each casino has these areas, catering to the high rollers who want privacy and perks. They're not waiting in line to cash tickets like other slot jockeys. Getting on a machine isn't as difficult. A staffer is ready to take their tickets at any moment. It's full-service gambling.

The machines have adjustable seats, making you comfortable while the grind goes on and the casino rests on its mathematical advantage. The lights are dimmer, but the screens are bright. Dream big or go home. Most players spend hours there.

The games are the same, no matter the denomination. A 9-6 Jacks-or-better machine at $100 plays the same as a 9-6 Jacks-or-better machine at $1.

At the Four Queens Hotel and Casino in downtown Las Vegas, Bruce Copland, 65, has been playing multi-hand video poker, a game that allows him to bet a penny per hand. The highest payout is 4,000 nickels if he manages to get a royal flush.

He once put $25 dollars into a video poker machine and walked out $20,000 richer.

"That was 25 years ago," he said, chuckling.

But he still remembers it like yesterday.

On a Friday afternoon, the odds of recovering his losses were getting increasingly smaller as he kept losing money. Unsatisfied, he stood up and slowly made his way up from the blue leather chair. He moved over to another machine, this time betting a nickel.

It wasn't about getting that royal flush now, it was about breaking even.

Copland has been playing for more than 30 years, and helped developed two computer programs to show how to count cards at blackjack and win at video poker.

Winning, he admits, is still not an exact science.

Soon he was feeding another $200 into the machine. He'd lost half of his money already, but for the moment, optimism was trumping math.

"I'm going to make a profit here," he said.

The night wore on.

Almost nobody has offered any evidence that gambling losses played any role in the final madness that drove Paddock to load up his hotel suite with weapons — in part because no one, not Paddock's brothers, not his girlfriend, not his longtime former property manager — have been able to offer any theories at all.

"He spent decades acquiring weapons and ammo and living a secret life," Clark County Sheriff Joe Lombardo said last week. "Much of which will never be fully understood."