New York ? Jiverly Wong was upset over losing his job at a vacuum plant, didn’t like people picking on him for his limited English and once angrily told a co-worker, “America sucks.”

It remains unclear exactly why the Vietnamese immigrant strapped on a bulletproof vest, barged in on a citizenship class and killed 13 people and himself, but the police chief says he knows one thing for sure: “He must have been a coward.”

Jiverly Wong had apparently been preparing for a gun battle with police but changed course and decided to turn the gun on himself when he heard sirens approaching, Chief Joseph Zikuski said Saturday.

“He had a lot of ammunition on him, so thank God before more lives were lost, he decided to do that,” the chief said.

Police and Wong’s acquaintances portrayed him as an angry, troubled man who struggled with drugs and job loss and perhaps blamed his adopted country for his troubles. His rampage “was not a surprise” to those who knew him, Zikuski said.