SAN MARINO, Calif. — Saturday night was winding down at the Lai Lai Ballroom & Studio, with less than a half-hour to go until closing. There were three people left on the spacious dance floor.
Brandon Tsay, the third-generation operator of the family-run dance hall in Alhambra, was in the office off the lobby, watching the ballroom, when he heard the front doors swing closed and a strange clang that sounded like metallic objects hitting one another.
He turned around to see a semiautomatic assault pistol pointed at him.
“He was looking at me and looking around, not hiding that he was trying to do harm. His eyes were menacing,” recalled Mr. Tsay, 26, at his family’s San Marino home Sunday, less than 24 hours after he stared down a gunman who, unbeknown to him, had opened fire at another nearby ballroom, killing 10 people and injuring several others in one of California’s worst mass shootings.
About 20 minutes after that massacre, the gunman, who authorities identified as Huu Can Tran, 72, arrived at Lai Lai, just about two miles to the north, officials said.
Mr. Tsay struggled with the gunman and eventually disarmed him, saving countless lives and averting another tragedy. It was an act that officials roundly praised as heroic. Mr. Tran was found dead Sunday afternoon of a self-inflicted gunshot in a van about 30 miles away, according to law enforcement officials.
Mr. Tsay said the weapon the gunman was carrying signaled he intended to inflict maximum damage.
“How it was built and customized, I knew it wasn’t for robbing money,” Mr. Tsay said of the weapon. “From his body language, his facial expression, his eyes, he was looking for people.”
Sheriff Robert Luna of Los Angeles County said in a news briefing Sunday afternoon that “two community members” had disarmed the gunman at the Alhambra ballroom. “This could have been much worse,” he said.
But Mr. Tsay and his family, who reviewed the security camera footage from the lobby of the ballroom, said it was he alone who fought the gunman over control of the weapon and wrested it from him. The doors to the ballroom were closed and no one else was involved, they said.
“It was just my son. He could have died,” said his father, Tom Tsay, who said he was proud of his son for the bravery he showed. “He’s lucky, someone was watching over him.”
His older sister, Brenda, who currently runs the business, said the video showed a prolonged, fierce struggle between the two men all over the lobby.
“He kept coming at him, he really wanted the gun back,” she said of the gunman.
The younger Mr. Tsay, a computer coder who mans the ticket office a few days a week at the ballroom started by his grandparents, said it was around 10:35 p.m. Saturday that he turned to face the gunman, whom he didn’t recognize. He had never seen a real gun before, but could tell that it was a deadly weapon, he said.
“My heart sank, I knew I was going to die,” he said.
The next moment, he lunged and grabbed the weapon by its barrel and began wrestling with the gunman for control of it.
“That moment, it was primal instinct,” he said. “Something happened there. I don’t know what came over me.”
They fought over control of the gun for about a minute and a half, and it felt like they were similarly matched in strength, Mr. Tsay said. At one point, the gunman looked down at the weapon and took one hand off it, as if to manipulate the gun to begin shooting. Mr. Tsay said he seized the moment and pried the pistol away from the man.
He pointed the weapon back at him and yelled: “Go, get the hell out of here,” he recalled.
Mr. Tsay, who stayed up all night assisting police with their investigation, said he felt traumatized and hadn’t quite been able to process what he had been through. He particularly felt heartbroken for the community of Monterey Park and surrounding areas where his family and their ballroom had become established as a beloved haven over three decades, he said.
“Lai Lai,” a name his grandmother chose, means “come, come,” in Chinese, his sister said. The assailant, dressed in black, looked like he could easily be one of their regulars, he said.
“We have such a tight-knit community of dancers,” he said. “It feels so terrible something like this happened, to have one of our individuals try to harm others.”
Shawn Hubler contributed reporting.