It happened around 6:30 p.m. near 15th and Market streets.
According to Chief Inspector Scott Small, a 20-year-old man was sitting on a yellow dirt bike when a gunman exited a white vehicle and opened fire while chasing the victim.
"A male exits that vehicle and pulls a gun and starts chasing the victim south on the sidewalk in Centre Square by the famous Clothespin at 15th and Market," said Small.
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Small says the victim was shot in the face, neck and chest. He was rushed to an area hospital where he later died.
At least 11 shots were fired in this bustling part of the city.
"Right now, we do not have a motive for this homicide, but it clearly appears from the recording that the shooter was targeting this individual," said Small.
The male suspect was able to get away. He is described as wearing a dark-colored sweatshirt, jeans and white sneakers. He is about 5'6" to 5'9" in height, according to police.
Small says no other injuries have been reported.
Anyone with any information is asked to call police at 215-686-TIPS