A doctor shot seven other people, one fatally, and tried to light himself on fire at Bronx-Lebanon Hospital before ultimately turning the gun on himself Friday afternoon, police say.

Officials say the shooter, 45-year-old Dr. Henry Bello, who used to work at the hospital, entered the building wearing a lab coat with an AR-15 concealed inside. He began firing at 2:50 p.m. and a short while later, police say he fatally shot himself. One victim was killed and six others were injured at the hospital.

The person who was slain was a female doctor who was found on the 17th floor.  She has been identified as Tracy Sin-Yee Tam. Six additional victims were found wounded on the 16th floor. Five of those victims were physicians and medical students, and one was a patient, who was shot in the leg.

Hospital officials say the 16th and 17th floors are surgical floors where Bello used to work.

One of the victims, a medical student, underwent brain surgery and remains in critical condition. One of the injured physicians is being transferred to Mount Sinai Hospital to undergo liver surgery, and the other three victims are in stable condition.

The hospital said Bello quit as a family medicine doctor in 2015 in lieu of being fired. Officials declined to explain why, but it is believed sexual harassment may have been involved. After he was forced to resign, he allegedly told colleagues he would be back to kill them.

The Daily News says it received an email from Bello just hours before the deadly shooting began. In the email, Bello called out two doctors by name and blamed them personally for his termination from the hospital, according to the newspaper.

Bello stated he was ultimately forced to resign and blocked from obtaining a medical license because of threats made to a co-worker.

"We had a tragedy here in the Bronx this afternoon," Mayor Bill de Blasio said at a news conference outside the hospital. "I want to say at the outset, thank God this was not an act of terrorism...It appears to be a work-related matter, but that makes it no less tragic."

A man connected to the hospital told News 12 that an initial alarm went off related to a report of a fire, which resulted in the automatic shutoff of elevators in the hospital. That meant there was only stairway access when an alert system announced an active shooter event to hospital personnel just minutes later.

NYPD Commissioner James O'Neill said the suspect apparently attempted to set himself on fire, activating the fire alarm.

By Friday evening, officials said the hospital was once again fully operational, and a lockdown had been lifted, with the exception of on the 16th and 17th floors.

"There's smoke, there's water, there's blood everywhere -- you have to wade through that," said Dr. Sridhar Chilimuri, the chairman of the hospital's Department of Medicine, who praised his colleague's quick reactions to the shooting.

The chief physician for the hospital said that the bravery of the staff was the reason that only one patient suffered a minor injury. That patient is expected to be released soon.

Hospital staffers said training exercises helped prepare them for the situation.