He was a high-stakes gambler recognized in the casinos of Nevada. He dabbled in real estate investments in Texas. His last known full-time employment was 30 years ago. He was twice divorced. He had a pilot’s license and had owned two single-engine planes.

While his motive for the mass shooting outside a Las Vegas casino on Sunday night is unknown, details of Stephen Paddock’s history pointed to an unmoored and highly unconventional life.

From his neighbors in a quiet retirement community in Mesquite, Nev., he drew little attention, unless it was for his extreme propensity to keep to himself. He displayed no strong religious or political views, his relatives said, and was not known for angry outbursts.

But he was the son of a bank robber who ultimately escaped from prison and spent most of the 1970s on the F.B.I.’s most wanted list. His girlfriend, sought for questioning by law enforcement officials after the shooting, had passed through Tokyo, officials said.

Details about Mr. Paddock’s career and livelihood were sparse, aside from observations by neighbors and family members that he routinely gambled large amounts of money. “He was a gambler, that was his job,” his brother, Eric Paddock, told reporters Monday at his home in Orlando. “He was a wealthy guy, playing video poker, who went cruising all the time and lived in a hotel room.”

Image Stephen Paddock in a photo provided by his brother Eric Paddock. Credit... via Associated Press

Mr. Paddock and his three brothers were raised by their mother, who told the children that their father had died when in fact he was in prison, Eric Paddock said. Mr. Paddock’s father was convicted in 1961 of committing a series of bank robberies, and was sentenced to 20 years, but escaped from La Tuna federal prison in Texas in 1968 and then became a used-car dealer and bingo parlor operator in Oregon.

A “Wanted” poster for the elder Mr. Paddock warned that he was “diagnosed as psychopathic,” “reportedly has suicidal tendencies” and “should be considered armed and very dangerous.”

The children’s mother was left to raise the family on her own. They moved around the country, from Iowa to Tucson to Southern California, another brother, Patrick Paddock II, of Tucson, said. Stephen Paddock’s behavior did not offer any indication of violent tendencies, the brother said.

“He was the least violent in the family during my childhood. So, it’s kind of like, ‘Who?’ ” Comparing himself to his brother, he said, “I have much more anger.”

Stephen Paddock attended college, his family said, and worked for a predecessor company to Lockheed Martin, the aerospace contracting company, from 1985 to 1988. Lockheed Martin confirmed his employment but did not identify the company for which Mr. Paddock worked.

Mr. Paddock once owned and managed a working-class apartment complex in the Dallas suburb of Mesquite, Tex., records show.