Here’s what we know about the suspected gunman.

LOS ANGELES — As grieving families received news of lost loved ones in a massacre at a popular dance hall, investigators were looking on Monday into the suspected gunman’s background and whether he might have been driven by personal animosities when he shot 20 people, 11 of them fatally, at the Star Ballroom Dance Studio in Monterey Park, Calif., on Saturday night.

The suspect was found dead of a self-inflicted gunshot in a white van on Sunday after a long manhunt across Southern California. Here is what we know about him.

He was 72, divorced and a naturalized U.S. citizen.

The authorities identified the suspect on Sunday as Huu Can Tran, 72. An immigration document indicated that Mr. Tran was born in Vietnam, and property records showed he likely emigrated to the United States in the late 1980s. He became a U.S. citizen in 1990 or 1991, according to the immigration document. Court records indicate that he was married in June 2001 and divorced in May 2006.

He attempted a second attack but was thwarted, the police say.

The authorities said that, after carrying out the massacre at the Star Ballroom, the gunman went to another dance venue, the Lai Lai Ballroom & Studio in the neighboring city of Alhambra.

As he entered, he was confronted by Brandon Tsay, whose family owns the ballroom. Mr. Tsay said he struggled with the gunman and was able to disarm him. The gunman then fled.

“He was looking at me and looking around, not hiding that he was trying to do harm,” Mr. Tsay said in an interview at his home in San Marino Sunday night. “His eyes were menacing.”

Investigators are focusing on whether he was seeking particular people.

The authorities have not publicly identified a motive in the attack. But as investigators interviewed witnesses on Monday, they were focusing on the theory that the attack was personally motivated, and that the suspect had gone to the studio with specific targets in mind, according to a law enforcement official briefed on the matter. Detectives think he may have been “looking out for specific people for a specific reason,” the official said.

The suspect probably knew some of the 11 people he killed, while others may have been randomly shot, according to the official.

Investigators are also seeking to determine whether the suspect may have visited the second ballroom in search of people he wasn’t able to find at the first, the official said. The two studios attract the same clientele of dance enthusiasts, and investigators believe that some people visited both venues on Saturday night.