Two police officers and four civilians have been injured - and a suspect shot dead - after a chase and shootout through the streets of west Philadelphia.
Police Commissioner Richard Ross said Sergeant Sylvia Young was ambushed late on Friday and shot a number of times in the arm and protective vest.
Mr Ross also said Ed Miller, a former police officer who is now a member of the police force at the University of Pennsylvania, was also wounded.
Both are in a stable condition at Penn Presbyterian Hospital.
Two of the four civilians who were injured are in a critical condition, Mr Ross said.
The suspect was cornered in an alley and fatally shot by police, the commissioner added.
Ms Young, a 19-year police veteran, was sitting in her vehicle at about 11.20 pm when she was ambushed by the suspect, who fired numerous shots, Mr Ross said.
She was struck up to eight times in her protective vest and left arm.
The suspect fled and shot into a nearby bar, striking a security guard in the leg. The man then grabbed a woman and used her as a shield before shooting her in the leg.
Moments later, as police gave chase, the suspect shot into a car, striking a man and a woman in the chest. Mr Ross said they are both in a critical condition.
Mr Ross said Mr Miller and two police officers chased the man into an alley, where he was shot and killed.
The identities of the suspect and the others who were injured were not immediately released.