The suspected gunman who authorities say killed 11 people Saturday night at a crowded dance studio in Monterey Park, California, was a regular at the studio who "couldn't get along well with people," an acquaintance told ABC News.
Authorities said the suspect, identified as 72-year-old Huu Can Tran, fled the scene of the shooting and traveled to nearby Alhambra, where he allegedly entered a second dance hall before being disarmed there and again fleeing.
The next day police found him dead from a self-inflicted gunshot wound inside a van in Torrance, about 30 miles southwest of Monterey Park, according to authorities.
Tran, who was from Riverside County, appears to have been a professional trucker for at least 20 years. He was briefly the chief executive officer of a San Gabriel-based business called Tran's Trucking Inc., established in 2002 and dissolved in 2004, according to incorporation filings.
Los Angeles County Sheriff Robert Luna said during a press briefing on Monday that the suspect has "limited criminal history," including an arrest in 1990 for an unlawful possession of a firearm.
Investigators working to determine a motive for the shootings are looking into whether domestic violence played any role, according to sources.
CNN, which spoke with the ex-wife of Tran, reported that she said she met Tran two decades ago at Star Ballroom Dance Studio, where the shooting took place.
According to the woman, who asked not the be identified, "he could be quick to anger," but would not get violent.
A senior law enforcement official briefed on the matter told ABC News that investigators are searching for a motive, including reports that Tran might have been targeting his ex-wife. But it is unclear if the shooter was targeting his victims, and law enforcement has not confirmed whether his ex-wife was at any of the locations or that she is a witness or victim.
According to a copy of the marriage license that the ex-wife showed CNN, Tran was an immigrant from China, CNN reported.
In 2005, Tran filed for divorce from his then-wife, according to court filings. A judge approved the divorce in 2006.
Pat Roth, Tran's neighbor in Hemet, said that Tran was "just a nice guy" and that "everyone around here thought he was just some quiet little guy," according to a video obtained by ABC News.
But Tran's former tenant and longtime acquaintance told ABC News Tran had "hate towards people."
The former tenant, who asked not to be identified, said Tran was a regular at the Star Ballroom Dance Studio as well as the Lai Lai Ballroom and Studio in Alhambra, where two people took a gun away from Tran following the Star Ballroom shooting.
He told ABC News that Tran liked to dance, but that he didn't have many friends at either of the dance studios. He said Tran "distrusted everyone" and could be characterized as paranoid.
"I wouldn't say he was aggressive, but he just couldn't get along well with people," he said.
He said Tran was a loner who spent his nights mainly by himself, but that he would offer women free lessons in the dance studio, which likely upset the owner and the staff instructors, who made their living on paid lessons.
"Probably, this made the instructors unhappy," he said. "I think there was tension between Tran and those instructors."
ABC News' Josh Margolin and Alex Stone contributed to this report.