At least three doctors were shot at Bronx Lebanon Hospital this afternoon by a gunman in a lab coat.
The incident began unfolding at around 2.45pm at the medical center on Grand Concourse in the Morris Heights section of The Bronx.
Police sources say a gunman dressed as a doctor opened fire on the 16th floor of the hospital and shot multiple people.
Just before 4pm, J Peter Gould, an NYPD spokesperson, tweeted: 'One shooter is deceased at the hospital.'
'Active shooting in Bronx Leb. Two confirmed shot. Man dressed all in black. Smoke from the 16th floor,' the NYPD Special Operations Division tweeted an hour prior.
Heavily armed NYPD units were dispatched to the scene and proceeded to scour the building in search of the suspect.
The New York Daily News reported that a trail of blood was found leading from the second to the eighth floor.
The gunman was believed to be barricade in the 16th floor.
An FDNY official tells the New York Times the shooting victims were doctors. Their conditions are unknown at this time.
Police described the suspect in a radio transmission as a tall, thin man in a blue shirt and a white lab coat.
An NYPD official tells the paper there are unconfirmed reports circulating that the wanted shooter is an employee - or a former employee - of Bronx Lebanon.
Television images showed the hospital surrounded by police cars and fire trucks. Police could be seen on the roof of the building, at one point, with their guns drawn.
Bronx-Lebanon Hospital Center describes itself as the largest voluntary, not-for-profit health care system in the south and central Bronx.
The 120-year-old hospital claims nearly 1,000 beds spread across multiple units. Its emergency room is among the busiest in New York City.
The hospital is about a mile and a half north of Yankee Stadium.