Paddock used the perks liberally, indulging in limousine rides, spending complimentary cash on Swarovski crystal jewelry in casino gift shops, and staying in free hotel rooms and suites. His family members have said he considered casinos as a second home and gambling a retirement profession.

Much is still unclear about Paddock's gambling history, but it is clear that casinos in various cities were a big part of his life. They also were a central aspect of his final act: He carried out the deadliest shooting rampage in modern U.S. history from a luxury suite on the Mandalay Bay Resort and Casino's 32nd floor, from which he shot and killed dozens of people and wounded more than 500 on Sunday. As police closed in on his room, he used one of 23 guns he had with him to shoot himself in the mouth.

He died in the suite — high above the Las Vegas Strip and the casino floor — surrounded by guns, bullet casings and blood.

Those who knew Paddock are perplexed by the extreme violence, but not by his presence in a Las Vegas casino that night. Dealers, waitresses, security guards, bartenders, drivers and family members said Paddock was a committed gambler who spent much of his time in casinos, playing their slots and video poker games and living in their hotels sometimes for m

onths at a time.

A person familiar with Paddock's gambling history, who spoke on the condition of anonymity, said Paddock was considered a midrange gambler whose wins and losses were in the tens of thousands of dollars — placing him in the middle tier of VIP programs for loyal gamblers.

"This is a man who clearly enjoyed gambling. He is someone who won and lost money through the years. He paid all of his bills and did so on time ... never having any sort of incident," the person said. "He has the profile of a responsible gambler."

Paddock frequented casinos in Reno, Nev., where he recently bought a home in a new retirement subdivision. He met his girlfriend, Marilou Danley, several years ago while she was working as a high-limit hostess for Club Paradise at the Atlantis Casino Resort Spa, known as the highest-end casino in Reno, said Paddock's brother, Eric Paddock. The two used to gamble side by side.

Casino employees in Reno were used to seeing Paddock and Danley roll up to the Atlantis in a limo before a night of play. She was friendlier; he was more taciturn. Sometimes they came together, sometimes alone, said employees who worked at casinos across Reno, speaking on the condition of anonymity because casino managers had ordered them not to discuss Paddock publicly.

Danley arrived in Los Angeles on Wednesday after returning from a trip to the Philippines. She spoke with FBI agents there and issued a statement through her attorney saying that she knew Paddock as a "kind, caring, quiet man" whom she loved. She said she knew nothing of his plan for "violence against anyone."

A woman who worked with Danley at the Atlantis in Reno said Paddock had achieved the casino's highest loyalty-program status, which affords gamblers a host of privileges, including a personal casino host, premium seating at concerts and events, and complimentary carwashes — he also ordered meals off the restaurant menus and had them delivered to him as he gambled.

Eric Paddock said his brother essentially moved into the casino for months at a time.

The company that owns Atlantis said in a statement that it "had no current information regarding Stephen Paddock and Marilou Danley," noting that Danley stopped working there several years ago. "We are cooperating with law enforcement and support their efforts to investigate and address this tragedy."

Paddock also frequented other Reno casinos. He earned a reputation as a big spender at the Grand Sierra, and he was spotted in recent weeks at the Silver Legacy, where a dealer said he was known to wager $100 per bet on slot machines. A casino employee said Paddock was a frequent presence during the National Championship Air Races in September. Public records show that Paddock owned two planes and was a licensed pilot.

The gambling was, at times, apparently lucrative. Paddock's brother said he showed FBI investigators a text from Stephen Paddock saying he had won $250,000 at a casino.

"It's like a job for him. It's a job where you make money," said Eric Paddock, adding that his brother could lose $1 million and still have enough to live on.

Relatives said they believe Paddock was worth more than $2 million, making a small fortune from real estate deals and a business that he and Eric Paddock sold. Paddock told neighbors that he was a professional gambler but didn't show any trappings of wealth, driving nondescript cars and favoring khakis and polo shirts.

Eric Paddock recalled that his brother once arranged to take over the top floor of the Atlantis — all part of the free rooms, meals, drinks, spa services and other perks that lubricate the cash-sopped casino culture in Las Vegas, Reno and other gambling havens.

"RFB — room, food and beverage — is the most coveted comp," said David Schwartz, director of the Center for Gaming Research at the University of Nevada at Las Vegas.

Casinos closely track the habits of all but the most casual gamblers, monitoring the time they spend playing and the amount they wager. And they invest heavily in freebies and other inducements to keep them playing. Schwartz said that comps, on average, account for almost one-third of the expenses at Las Vegas's large casinos.

The 24 biggest Las Vegas Strip casinos had average expenses of $145 million in 2016, and comps accounted for $65 million of that total — more than payroll and taxes combined, according to a report by Schwartz's center at UNLV.

At the Mandalay Bay, a 1,450-square-foot, two-bedroom suite can rent for hundreds of dollars on a weeknight, according to the hotel's website, and can be worth far more than that depending on the season and events scheduled at the resort. Add in meals at high-end casino restaurants, tickets to shows, limousines, liquor and credits to spend on gambling, and comps can add up quickly.

"You don't have to be the highest roller, and they still take care of you," said one Washington businessman who travels regularly to Las Vegas.

Though offering a veneer of glitz and glamour, the comps allow casinos to promote and reward loyalty, analysts said, largely because casino officials know that the longer and more often a person gambles, the more likely it is that the house will win.

Comps serve a crucial function to casinos, making players feel important and keeping them at specific properties spending money. Free rooms help players stay in the casino and gamble as long as possible while they are there. The overall feeling of being a VIP entices people to return on a regular basis — and to feel as if they are getting something nearly guaranteed in return.

"If you're putting a lot of money into a slot machine and you're not getting anything back, at some point you're going to stop doing that," said Lia Nower, director of the Center for Gambling Studies at Rutgers University. "If they're getting free rooms and everything else, that's validation."

Nower said the rewards system differs with each casino ownership group.

"If you spend a decent amount of money, you go there a few times a year, you'd probably get comped rooms, meals, show tickets," she said. "If you're a high, high roller, you're getting suites, you're getting transportation, you're able to bring people with you."

Schwartz said casinos have sophisticated systems for tracking players' habits. Even fairly casual gamblers are encouraged to sign up for a "player card," essentially a loyalty club card that allows casinos to collect data about the time a gambler spends at a blackjack table or slot machine, the amount of their typical bet, and their overall winnings and losses. Inserting the card into a machine or handing it to a pit boss can allow players to accrue points that can used in a variety of ways.

A player who uses a loyalty card enough becomes a "rated" player and often qualifies for personalized service from casinos, including a "VIP host" who helps arrange for freebies, such as rooms, meals and show reservations. It also allows casinos to direct-market to players who are most likely to return, offering mailed and emailed coupons or discounts as enticements.

"They know the person has a set gambling budget, and they want to encourage loyalty," Schwartz said.

The cards are good at any casino owned by the same company. For example, an MGM Resorts player card is generally good at any casino in the chain, from the Mandalay Bay in Las Vegas to the MGM National Harbor near Washington, D.C.

Schwartz said different casinos distribute comps for different levels of spending. Someone who gambles $500 at premier Las Vegas casinos "might not get noticed" among gamblers who sometimes wager tens of thousands of dollars or more on a single hand.

But generally, he said, someone such as Paddock, who reportedly spent weeks at a time wagering tens of thousands of dollars or more, would qualify for high-end comps.

Nower said the comp system encourages people to keep coming back to their favorite venue, where they feel valued.

"There's a whole element of gambling that doesn't have anything to do with money. It's a sense of being important ... that comes with familiarity," Nower said. "People who know your name, people who know you're coming into town."

Dwoskin reported from Reno, Nev., and Zezima from Washington. Barbara Liston in Orlando, Fla., contributed to this report.