(CNN) The last time Eric Paddock heard from his brother, Stephen Paddock had texted to find out how their 90-year-old mother was doing.

It was mid-September and Hurricane Irma had cut power in the Orlando, Florida, neighborhood where she lived. Stephen Paddock, who lived in Nevada, followed up with a call to their mother. Later, he sent her a walker to help her get around, Eric Paddock said.

About two weeks after the text, 64-year-old Stephen Paddock would be dead of a self-inflicted gunshot after police say he opened fire on a country music festival in Las Vegas.

He was 'just a guy'

The news doesn't square with Eric Paddock's image of his older brother, he told reporters Monday -- a poker-playing accountant and real estate investor with no apparent political or religious affiliation, "as far as I know," he hastened to add.

To his brother, Stephen was "just a guy," an "army of one" with no known children despite a string of relationships. Someone you might see nursing a drink alone at a bar. Someone who went on cruises and played $100-a-hand video poker. Someone who sent boxes of cookies to his mother.

"There's absolutely no way I could conceive that my brother would shoot a bunch of people that he didn't know," Eric Paddock said outside his home, shaking his head as he fumbled for words.

"Something just incredibly wrong happened to my brother."

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Deadliest mass shooting in modern US history

Various agencies are investigating what led Stephen Paddock to shoot from the 32nd floor of the Mandalay Bay hotel into a crowd of some 22,000 concertgoers. Paddock killed 58 people and wounded nearly 500.

Las Vegas police said they did not know Stephen Paddock's name before the shooting and they believe he acted alone. He bought multiple firearms in the past, but investigators believe the firearms were purchased legally , a law enforcement official said. A Mesquite store, Guns & Guitars, said it sold a gun to Paddock and that "he never gave any indication or reason to believe he was unstable or unfit at any time."

Police found at least 23 weapons inside his hotel room, including multiple rifles, some with scopes. At least one rifle may have been altered to function as an automatic weapon, a law enforcement official said.

Stephen Paddock, in an undated photo

'We're up all night because we gamble'

Eric Paddock said he knew his brother had firearms. His children had gone skeet shooting with their uncle before, but Eric did not know Stephen to be a hunter.

Eric helped his brother drive across the country in 2016 to a new home in Mesquite, Nevada, a retiree community about 80 miles northeast of Las Vegas. Along the way, the brothers ate sushi and drank late into the evening, Eric Paddock recalled. But he did not recall his brother bringing a machine gun along with him.

However, he acknowledged the limits of his knowledge, living thousands of miles from a brother he only spoke to occasionally.

Stephen Paddock lived in Mesquite with his girlfriend, 62-year-old Marilou Danley. She was out of the country during the shooting, but returned Tuesday and was questioned by law enforcement.

He might have kept quiet about the guns, but he wasn't shy about the gambling.

When he bought a house in Mesquite, he wrote on his application that his income came from "gambling." He also told a real estate agent that he gambled about $1 million a year , an agent speaking on condition of anonymity said.

He sought privacy and kept a low profile. Some of his neighbors rarely saw him, but they knew he was a gambler.

Paddock said he was a high roller and real estate speculator from Las Vegas. "We're up all night because we gamble," Don Judy, one of Paddock's old neighbors in Florida, remembered him saying.

A search of Stephen Paddock's home in Mesquite turned up at least 19 additional firearms, explosives and several thousand rounds of ammunition, Clark County Sheriff Joseph Lombardo said Monday night. Several pounds of ammonium nitrate, a material used to make explosives, were found in Paddock's car.

That came as a surprise to one of his former neighbors. "If there was any impression, I would say, guy had no idea what a gun was," said Judy, who lived next door to Stephen Paddock from 2013-2015 in a retirement community in Melbourne, Florida.

Paddock never stayed at the house for very long, Judy said. Sometimes he came with his girlfriend, sometimes without.

Not a team player

Stephen Paddock held various federal jobs in the 1970s and 80s. He was a US Postal Service letter carrier in the mid- to -late 70s; an agent with the Internal Revenue Service from 1978 to 1984; and worked for the Defense Contract Audit Agency in 1984 and 1985, the US Office of Personnel Management said.

Eric Paddock said his brother also was a successful real estate investor who owned apartments and houses. Records link him over the years to more than nine houses, condos and apartment buildings in Nevada, Florida and California.

Investigators were looking Monday at several properties in the Reno area associated with Stephen Paddock.

Residents of the properties told CNN the FBI stopped by on Monday. One resident at a residence on Del Webb Parkway said he and his wife never saw Stephen Paddock, but saw his girlfriend as recently as this summer.

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Because he had no children, he was free to come and go as he pleased, his brother said. Paddock had married and divorced twice, court records show. His first marriage lasted two years, from 1977 to 1979. He remarried in 1985, and divorced again in 1990 after nearly five years of marriage.

His second ex-wife lives in Los Angeles County, California, and has had no contact with him in years, authorities said.

He flew planes for a while until he got tired of it and started taking cruises, his brother said. A federal official confirmed he had a pilot's license, but said that he was not up to date on the medical certification he would need in order to fly legally.

It was a passion that traced back to his childhood, his brother said. He excelled at sports, too, but never played or joined organized clubs. "He wasn't a team kind of guy," Eric Paddock said.

Father was bank robber

One point of intrigue has emerged from the shooter's background, courtesy of his brother: Their father was a bank robber.

Benjamin Hoskins Paddock

According to the FBI, Benjamin Hoskins Paddock was on its most-wanted list from June 10, 1969 until May 5, 1977. He escaped from prison in 1969 and lived on the run until 1978, when he was arrested in Oregon, the Eugene Register-Guard reported at the time. Eric Paddock said his father died a few years ago and that "he was never with my mom." Eric said he was born while his father was on the run.

But Eric Paddock resisted the idea that his brother was somehow emulating their father's criminal tendencies. When pressed to explain what happened, he has no explanation.

"He was my brother, and it's like an asteroid fell out of the sky," he said. "We're still just completely dumbstruck."

Correction: This story has been revised to give the correct full name of the Eugene Register-Guard. The story also has been revised to give the correct amount of time Stephen Paddock and his ex-wife were married. They were married for four years and nine months.