LOS ANGELES – A 26-year-old coder was about to close his family’s dance hall on Saturday when a man barged into his office and, with eyes that were “menacing” and an intention “to do harm”, pointed a semiautomatic pistol at him.

“My heart sank. I knew I was going to die,” Mr Brandon Tsay told The New York Times.

“He was looking at me and looking around, not hiding that he was trying to do harm. His eyes were menacing,” recalled Mr Tsay at his family’s San Marino home on Sunday.

He did not know then that the man, whom the authorities identified as Huu Can Tran, 72, had opened fire at another ballroom nearby just minutes earlier, killing 11 people and injuring several others.

Mr Tsay made a split-second decision. He chose to fight.

He lunged at Tran and grabbed the barrel of his gun. He eventually disarmed him, saving countless lives and preventing another tragedy.

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

Mr Tsay said he had never seen a gun in real life, but that it was clear Tran was not there to rob the place but to kill.

“From his body language, his facial expression, his eyes, he was looking for people,” he said.

Security footage showed Mr Tsay struggling with Tran for around 90 seconds before he was able to seize the gun from him.

Mr Tsay immediately pointed it back at Tran and yelled: “Go! Get the hell out of here!”

Tran fled. Hours later, he was dead, having shot himself inside a white van in Torrance on Sunday afternoon as police moved to arrest him.

Before he went to Lai Lai Ballroom and Studio, a business Mr Tsay’s family owned in Alhambra city, California, Tran had been to the Star Ballroom in Monterey Park, less than 5km away.

There, he killed five men and five women who were there with many others to celebrate Chinese New Year.

When he went to Lai Lai, it was already 10.35pm, and there were only three people left on the dance floor. There, Tran ran into Mr Tsay. AFP