A female doctor gunned down by an ex-colleague ousted from a New York City hospital was not his intended target, authorities have said.

A doctor forced out of a New York City hospital over sexual harassment claims returned with an assault rifle hidden under a lab coat and shot seven people, killing a woman medic and leaving several of her colleagues fighting for their lives.

Latest: The gunman who opened fire at a New York City hospital, killing at least one person, was a doctor who used to work there, a police official said.