The victim was also a doctor, a female physician. In photo: New York City Mayor Bill de Blasio speaks to the media outside of Bronx-Lebanon Hospital Center. Photograph: (AFP)
A former doctor at a New York hospital opened fire inside the building, killing one person and injuring six.
The former doctor had lost his job at the hospital.
The person he killed was also a doctor.
Five of the six people injured were reportedly hurt seriously.
The shooting occurred at the Bronx-Lebanon Hospital Center in the Mount Hope neighbourhood of the Bronx.
Mayor Bill de Blasio said several doctors were "fighting for their lives" following the incident in the Bronx borough north of Manhattan. He said the gunman, also a doctor and a former employee of the hospital, killed himself but gave no indication of his motive.Police suspect it was a workplace-related incident.
The gunman was found dead on the 17th floor of the hospital, with the dead doctor -- a woman -- lying nearby.
Reuters reported that the former doctor had stalked two floors of the hospital building in a white lab coat.
He was armed with an assault rifle and had tried to set himself on fire before finally shooting himself.
"Our hearts going out to the family of the doctor who passed away," New York mayor Mayor Bill de Blasio said, before praising rescue officials and the police force for their rapid response, as well as fire fighters for extinguishing a blaze that broke out.
America's largest city maintains a huge police deployment over fears of a potential terror attack like those that have hit European cities in recent years.
A pregnant woman who was undergoing a consultation on the 14th floor praised the way staff responded.
"I did as I was told and I'm safe and sound. They told us to go inside a room and hide. We were barricaded inside a room. The hospital staff was on top of everything. They were in control," Tamara told AFP, giving her first name only.
"I learned a long time ago: when you're pregnant, never panic," she added.
Nurse Patricia Phipps said the shooting did not come as a shock given the borough it took place in, The Bronx, which is known for its high crime-rate.
She said: "The neighborhood is sketchy. So you're not surprised sometimes these things happen when you work at hospitals like this. Things happen. That's just living in New York. I just said to myself: it's my turn."
The latest incident could also re-ignite debate over gun control laws in the United States, which sees more mass shootings than any other country.
Mayor De Blasio briefly touched on the topic in his press briefing, calling the attack "something we have seen around the country."
"Every time these things happen, it's another reminder that more needs to be done for those people that have access to these weapons...we can't continue not to do something about it," state legislator Marcos Crespo told news channel New York 1.
The last mass shooting occurred on June 14 near Washington DC when a man opened fire on a baseball team comprised of Republican congressmen, wounding four people including the chamber's third most senior member, Steve Scalise.
The gunman, James Hodgkinson, was shot dead by police.
(With inputs from agencies)