A gunman opened fire with an assault rifle inside a hospital in the Bronx Borough New York, killing one doctor and injuring six other people, five of them seriously.

The gunman, a former doctor at the hospital, killed himself in the attack.

Local mayor, Bill De Blasio said the shooting was isolated and appeared to be workplace-related.

He also said several of the injured are fighting for their lives.

The gunman has not been officially named but police sources told US media he was Henry Bello, a former family-medicine doctor at the hospital.

Sources quoted by NBC said he had resigned in 2015 in lieu of termination.

Mr O’Neill said the gunman had tried to set himself on fire and died of a self-inflicted wound.