The lone gunman who killed 13 people and himself at an immigrant center in Binghamton, N.Y., Friday may have been depressed after losing his job and upset about his poor English skills, the city's mayor says.

The shooting began at around 10:30 a.m. when police say 42-year-old Jiverly Voong, of Johnson City, walked into the American Civic Association after blocking the building's back entrance with his van and opened fire.

Sources say at the time of the incident the center was conducting an immigration test. At least 41 hostages were trapped inside the building. Nearby apartments were evacuated.

"There's absolutely no reason for this kind of shooting and brutal attack of innocent people," said Gov. David Paterson during a press conference Friday.

Authorities have seized three computer hard drives, a brown canvas rifle case, a briefcase, a small suitcase and several paper bags from Voong's home.