(CNN) — The death toll in Saturday’s mass shooting at a dance studio in Monterey Park, California, rose to 11 on Monday as investigators searched the gunman’s background for an explanation as to the massacre.

Authorities initially said 10 people were killed in the shooting at the Star Ballroom Dance Studio and that at least 10 were hospitalized. LAC+USC Medical Center, which treated four of the 10 wounded, said Monday that one had died.

“Our heroic staff at LAC+USC Medical Center have worked tirelessly to care for the four victims entrusted to our care. Unfortunately, despite our best efforts, we are saddened to share that one of the victims has succumbed to their extensive injuries. We want to express our deepest sympathies to their families and loved ones,” the hospital said.

The additional death comes as investigators pore into the history of the 72-year-old gunman, Huu Can Tran, who opened fire on revelers celebrating Lunar New Year in the majority-Asian American city.

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Afterward, Tran went to another dance studio in nearby Alhambra, but was tackled and disarmed by heroic civilians. He fled the scene and police found him a day later in a white van about 30 miles away in Torrance, dead from a self-inflicted gunshot wound.

The bloody whirlwind transformed one of the most auspicious days of the calendar for Asian Americans into a day of unfathomable tragedy, yet still one which could have been even deadlier.

There are as yet few clues as to the motivation of the shooter, an elderly Chinese immigrant described as having an interest in dance and a hot temper.

Investigators found a handgun as well as “several pieces of evidence” in Tran’s white van linking him to the Monterey Park and Alhambra dance studios, Luna said.

The Los Angeles County Sheriff’s Department got a search warrant for Tran’s home in The Lakes at Hemet West, a senior community about 80 miles east of Monterey Park, a Hemet Police spokesperson confirmed.

Hemet Police also said Tran had visited the police department two weeks ago and made serious allegations of wrongdoing.

“Tran visited the Hemet Police Department lobby on January 7 and 9, 2023, alleging past fraud, theft, and poisoning allegations involving his family in the Los Angeles area 10 to 20 years ago,” police said in a statement. “Tran stated he would return to the station with documentation regarding his allegations but never returned.”

In carrying out the attack, he used a semi-automatic assault pistol with an extended large-capacity magazine, authorities said. A law enforcement official told CNN it was a Cobray M11 9 mm semi-automatic weapon. The weapon, which had been disarmed at the Alhambra dance studio, was traced to the suspect, giving authorities his name and description.

All of the 10 people initially reported as dead — five men and five women — were over the age of 50, and nine were in their 60s and 70s. Among those slain were My Nhan, 65, and Lilan Li, 63, the Los Angeles County coroner’s office said Monday.

The massacre, one of at least 36 mass shootings in the US so far this month, particularly targeted members of the Asian community, who have faced a surge of deadly attacks and harassment since the start of the Covid-19 pandemic. About 65% of residents in Monterey Park are of Asian descent and some 100,000 people from across Southern California typically turn out for Lunar New Year celebrations.

“I’ve lived here for 37 years, and I could never have imagined such a terrible thing happening,” Rep. Judy Chu, who represents Monterey Park in Congress, told CNN on Sunday. “This is a tight-knit community and it has been very peaceful all these years. So that’s why it is even more shattering to have this happen.”

Civilian who disarmed gunman speaks out

When police arrived at the Monterey Park dance studio, “they came across a scene that none of them had been prepared for,” city police chief Scott Wiese said. The killer had inflicted “extensive” carnage before fleeing the scene.

A few miles away in Alhambra, Brandon Tsay was working the ticket office of the Lai Lai Ballroom & Studio, unaware of the massacre. Then, the same gunman entered the business his family had owned for three generations.

“From his body language, his facial expression, his eyes, he was looking for people,” Tsay told The New York Times.

“He was looking at me and looking around, not hiding that he was trying to do harm,” he said. “His eyes were menacing.”

The gunman pointed a semi-automatic weapon at Tsay — the first gun he had seen in real life — he told the Times.

“My heart sank,” he said, “I knew I was going to die.”

Tsay struggled with the man for about a minute and a half and eventually wrestled the gun from him when the man took his hand off it, he told the Times.

“That moment, it was primal instinct,” he said. “I don’t know what came over me.”

Once Tsay gained control of the gun, he told the Times, he pointed it back at the suspect and yelled for him to “get the hell out of here.” The man fled.

“The suspect went to the Alhambra location after he conducted the shooting (in Monterey Park), and he was disarmed by two community members who I consider to be heroes,” Los Angeles County Sheriff Robert Luna said. “They saved lives. This could’ve been much worse.”

Suspect used to frequent the dance hall, sources say

Tran had once been a familiar face at the Star Ballroom Dance Studio, where he gave informal dance lessons, three people who knew him told CNN. But it’s not clear how often he visited in recent years, if at all.

He even met his ex-wife there about two decades ago after he saw her at a dance, introduced himself and offered her free lessons, the ex-wife said.

Tran worked as a truck driver at times, his ex-wife said. He was an immigrant from China, according to a copy of his marriage license she showed to CNN.

The two married soon after they met, according to the ex-wife, who asked not to be named due to the sensitivity of the case.

And Tran had a hot temper, his ex-wife and others said.

While he was never violent to her, the ex-wife said, Tran would get upset if she missed a step dancing because he felt it made him look bad.

Tran filed for divorce in late 2005, and a judge approved the divorce the following year, Los Angeles court records show.

Another longtime acquaintance of Tran also remembered him as a regular patron of the dance studio. The friend, who also asked not to be named, was close to Tran in the late 2000s and early 2010s, when he said Tran would come to the dance studio “almost every night” from his home in nearby San Gabriel.

At that time, Tran often complained that the instructors at the dance hall didn’t like him and said “evil things about him,” the friend recalled. He said Tran was “hostile to a lot of people there.”

More generally, Tran was easily irritated, complained a lot and didn’t seem to trust people, the friend said.

Tran’s friend was “totally shocked” when he heard about the shooting, he said, noting he hadn’t seen Tran in several years.

“I know lots of people, and if they go to Star studio, they frequent there,” the friend said. He said he was “worried maybe I know some of” the shooting victims.

Monterey Park mass shooting kills 11, gunman’s motive still unknown