At least two people were shot in the incident, which began at 2.50 p.m. (local time) at 173rd Street and Grand Concourse in the Mt. Eden section, CBS News reported.
The gunman, who is believed to be a former employee and was described as wearing a white lab coat, was said to be armed with a rifle.
Four to six people were shot in the incident, and other people suffered minor injuries while attempting to get away.
The extent of the injuries of the other shooting victims wasn't immediately clear.
Police went floor by floor searching for the shooter while the hospital has been surrounded by emergency response vehicles.
A 'red alert' went off within the hospital, which was placed on lockdown. Doctors and nurses barricaded themselves within.
Bronx-Lebanon Hospital Center, a 120-year-old facility, claims nearly 1,000 beds spread across multiple units. Its emergency room is among the busiest in New York City.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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