ARMED DOCTOR ATTACKS A NEW YORK HOSPITAL.

A doctor harboring what appeared to be a longstanding grudge opened fire with an assault rifle at the New York City hospital where he used to work Friday, killing one and injuring several others before taking his own life, according to police sources.

In the wake of what New York City Mayor Bill de Blasio called a “horrific” instance of what appeared to be workplace violence just before 3 p.m., the suspect, Dr. Henry Bello, who hid the AR-15 under his lab coat, tried to set himself on fire and then shot himself in the head, the sources said.

“Our hearts go out to the family of the doctor who passed away,” Mayor de Blasio said, adding that the city stands in “solidarity” with those who were “fighting for their lives.”

Hospital workers described a terrifying scene as well as heroism amid the chaos, according to ABC-owned station WABC.

EMT Robert Maldonado said he and his partner had locked themselves in a room with doctors and nurses when they heard someone yell for medics, according to WABC.

When they ran out, they found a doctor shot in the stomach, the station said.

“He was in a lot of pain obviously. We carried him nine floors. The police department helped carry, I helped put pressure on the wound, the entrance and exit wound and the police department they all just grabbed his legs, grabbed his arms,” Maldonado said, according to WABC.

Police sources said the alleged killer, who resigned from Bronx-Lebanon Hospital in 2015 over allegations he sexually harassed a co-worker, went to the 16th floor of the hospital looking for the doctor against whom he had the grudge.

When he was told that the doctor wasn’t there, Bello opened fire, the sources said, wounding six.

He then went to the 17th floor, where he encountered a female doctor in a hallway and fatally shot her, according to the sources.

Bello then attempted to set himself on fire and then shot himself in the head, sources said.

Three of the injured were in critical condition.

According to the police sources, Bello had four prior arrests, the most serious for sex abuse in Greenwich Village in August 2004, when he lifted a 23-year-old woman up by her crotch outside a Bleecker Street building.

He pleaded guilty to unlawful imprisonment, a misdemeanor, and was sentenced to community service, the sources said.

Bello was also charged with unlawful surveillance for allegedly peeking under a victim’s clothing in October 2009, according to the sources. In 2003, he was charged with fare beating and burglary.

Further details on those cases as well as their statuses was not clear.

A spokesman for Bronx-Lebanon, Errol Schneer, told the New York Times that Bello was hired in August 2014 and the hospital wasn’t aware of his criminal record at that time.

Bello was a Nigerian national who went to medical school in the Caribbean, according to sources. He was not a licensed doctor in the U.S. but working under a limited state-issued permit. He had previously been issued a pharmacy technician license in California in 2006, around the time he was at University of Southern California, sources said.