A faster response by police to the attack at an immigrant services centre in the United States would not have saved any lives, a county prosecutor said..

IMMIGRANT centre gunman Jiverly Wong was upset over losing his job, people picking on him for his limited English and once angrily told a co-worker that he hated America.

Investigators were trying today to find out why a gunman killed 13 people at an immigration centre before apparently shooting himself.

Up to 13 people were killed and 26 others injured when a man armed with a high-powered rifle opened fire in New York today, according to US reports.

At least four people were shot and dozens taken hostage by a man armed with a high-powered rifle in New York, US officials said today.