A nurse at a Philadelphia hospital fatally shot his co-worker early Monday and fled the scene in a U-Haul truck before wounding two police officers in a gunfight, authorities said.

The 55-year-old nurse, whose name was not immediately released, was wearing scrubs when he shot his co-worker on the ninth floor of Thomas Jefferson University Hospital just after midnight, Philadelphia Police Commissioner Danielle Outlaw said at a news conference.

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Investigators said the 43-year-old co-worker, who was a certified nursing assistant, was shot six times, FOX29 Philadelphia reported. He was later pronounced dead.

Police said it was unclear what sparked the shooting, but believe that the victim was targeted. Investigators are looking into the background of both men.

After the shooting, the gunman fled the hospital in a U-Haul box truck. Police were alerted to the suspect’s location about an hour later after a passerby waved down officers near a school.

A nurse at a Philadelphia hospital fatally shot his co-worker early Monday and fled the scene in a U-Haul truck before wounding two police officers in a gunfight, authorities said.

The suspect squared off with four police officers in a gunfight about an hour after the shooting. Dozens of evidence markers could be seen at the scene Monday. (FOX29 Philadelphia WTXF)

Outlaw said that the passerby told the officers that a man in scrubs armed with a long gun appeared to be firing shots into the air.

Four officers spotted the suspect and observed him wearing body armor, and in possession of several weapons including a rifle and a semi-automatic handgun, Outlaw said.

The gunman opened fire on the officers, and all four fired back, the commissioner said. The suspect fired 55 to 80 rounds during the shootout, FOX29 reporter Steve Keeley tweeted.

Two officers were struck — one suffered an elbow wound that will require surgery while the other was grazed on the nose. The officers' wounds weren't considered life-threatening.

A nurse at a Philadelphia hospital fatally shot his co-worker early Monday and fled the scene in a U-Haul truck before wounding two police officers in a gunfight, authorities said.

Officers observed the suspect wearing body armor, and he had several weapons including a rifle and a semi-automatic handgun. The suspect reportedly fired 55 to 80 rounds at four responding police officers. (FOX29 Philadelphia WTXF)

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The suspect was shot in the upper body and neck. He was in critical condition but expected to survive. 

Police are continuing to investigate the shooting.

The Associated Press contributed to this report.