Both homicide detectives and internal affairs are investigating what happened around 6:30 p.m. in an alley near 56th and Walton streets.
It started when a pair of uniformed officers in a marked car attempted to stop a tan car with a driver and two passengers inside.
When the officers began to question the driver, the front seat passenger took off running.
Lt. Ray Evers of the Philadelphia Police Department says the male passenger ran through one alley, across Pemberton Street, and into another alley.
In the alley, which is about three-feet wide and filled with brush and debris, police say the suspect grabbed for the officer's baton and Taser.
"There was struggle over his Taser, and during that course of the actual struggle between the Taser and the officer's weapon, they were close, they were within a foot of each other and that's when the officer discharged three times," Evers said.
Two bullets struck the suspect, identified as a man in his 20s, in the chest. He was pronounced dead about 15 minutes later.
No weapons were found on him or in the alley.
Meantime, during the chase and shooting, the driver of the car took off.
"The car was described as a tan Ford took off from the area; we are still looking for the Ford," Evers said.
The backseat passenger was being interviewed by police Thursday night.
The officer involved in the shooting will be placed on desk duty until the internal affairs investigation is complete.