WASHINGTON >> The man suspected of the deadliest shooting spree in U.S. history was described as a high roller, but authorities could not immediately determine if his gambling luck had gone way south.

Las Vegas casino records suggest that Stephen Paddock could actually have won tens of thousands of dollars in the weeks before he fired hundreds of rifle shots from a 32nd-story hotel window at a throng of country music fans below, a casino executive and a federal law enforcement official said today.

But he also could have suffered big losses during the same period. That’s one reason the FBI was still stumped late today on what led him to sneak an arsenal of rifles and ammo into his Mandalay Bay hotel room and unleash a murderous barrage of gunfire Sunday night, killing at least 59 people and wounding 527 more before taking his own life.

Paddock’s brother was quoted as saying he was wealthy, liked to take cruises, gamble and go to shows in Vegas.

In the weeks before the massacre, Paddock filled out several required federal financial reports signaling that he either had won more than $10,000 in a single gaming day or laid out a sum larger than that at the casino, said the federal law enforcement official, who spoke on condition of anonymity because the investigation is confidential.

NBC News, which first reported on Paddock’s large transactions, said some of the Currency Transaction Reports, or CTR, recorded movements of funds exceeding $20,000 and even $30,000.

Under a provision of the Bank Secrecy Act, if someone plunks down $11,000 in cash at a casino’s roulette wheel, the casino is required to fill out a CTR because the sum exceeds the threshold of $10,000. The reports, which also are required if multiple transactions together top $10,000 on a single gaming day, are turned over to the U.S. Treasury Department’s Financial Crimes Enforcement Network and the Internal Revenue Service.

But the reports are not required if a gambler loses more than $10,000. If Paddock lost heavily and didn’t file transaction reports, investigators still might be able to track his gambling fortunes by watching hours of casino videos that record every bet at gaming tables.

Paddock lived in a modest home in nearby Mesquite, Nev., but had earlier lived in a town of the same name outside Dallas. He had investments in several real estate deals, including an apartment building in Mesquite, Texas, and an uncompleted real estate development in Henderson, Nev., south of Las Vegas. In both cases, Peggy Paddock, which matches the name of his ex-wife, was listed among investment partners. Paddock also had owned two propeller airplanes, though he sold them several years ago, public records show.

Paddock had 16 guns in his hotel room when his body was found by police, according to law enforcement authorities; another 18 were found at his home, they said, plus various explosives, including ammonium nitrate, a common fertilizer that can be turned into a bomb.

Christopher Sullivan, general manager of the Las Vegas retailer Guns & Guitars, said Paddock “was a customer and purchased firearms from our store” but “never gave any indication or reason to believe he was unstable or unfit.”

He said that “all necessary background checks and procedures were followed, as required by local, state and federal law.”

Sullivan, who said his store is cooperating with investigators, said he and his employees “mourn for this tragedy” and offer their prayers to the victims and their families.

Property records show that Paddock had lived with Marilou Danley, whom his brother, Eric, described as his girlfriend when speaking to reporters outside his Orlando, Fla., home.

A friend of Danley’s, Cherie Geronimo-Carithers, told McClatchy she met Paddock a handful of times through her sister, who socialized with the couple and was “very close” with them. She said her sister, Veved Geronimo-Larot, who met Danley because they both worked at the Atlantis Casino, “is devastated.”

On her LinkedIn page, Marilou Danley calls herself simply a “Gambling & Casinos Professional at Atlantis Casino Resort Spa” in Reno. The page said she was a “high limit hostess” from 2010 to 2013 at the casino. On its web page, Atlantis touts its “high limit” area as a private section for special gamblers.

Paddock and Danley came to her father’s 70th birthday party six years ago, Carithers said.

“They seemed very close,” she said. “To me, it felt like she was in love with him.”

Carrithers said that she and her sister assumed Paddock had investments and that money was not an issue.

But, she said, Paddock was a high-stakes gambler.

“Everybody has demons, but it’s hard to believe” that he was responsible for the mass shooting, she said.

Reached by McClatchy, the sister, who said she was “still processing” the news, said “I am friends with both of them, but I don’t want to comment now.”

The FBI quickly shot down a claim by the Middle East Islamic terrorist group ISIS that Paddock had converted to Islam several months ago and carried out the attack at its behest.

Fateen Seifullah, imam of Masjid As-Sabur, Las Vegas’ oldest mosque, expressed relief that law enforcement agencies moved quickly to reject the Islamic State’s claim.

“If the sheriff and FBI hadn’t come out so clearly saying he had no Muslim affiliations,” he said, ” … I’m sure we would’ve had some problems.”

“My heart hurts and my head hurts. We (the Muslim community) haven’t found any reason to do anything except join the rest of Las Vegas in mourning and grieving.”