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 Binghamton 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 on Saturday.