Attorney Eric Birnbaum didn't have a chance, police say.
He was ambushed as he got out of his car Wednesday morning to walk into work.
The 51-year-old personal injury attorney was shot once in the back of the head.
Authorities say they don't have much to go on, only a partial description of a white man wearing a knit cap and sunglasses.
Birnbaum was taken to St. Mary's Medical Center where he died Wednesday afternoon.
Friends of Birnbaum talked glowingly about the father of two.
"No one disliked the man. He was a great man," said Frank Iocco.
Northampton Township police and the District Attorney's office are investigating. The D.A. said they took a person of interest into custody for questioning, but didn't elaborate.
Investigators visited the victim's home in Northeast Philly Wednesday evening, removing a computer.
Police were handing out 1,400 flyers around the shopping center Thursday and spoke with pedestrians and motorists, hoping to learn more about what happened in the shooting.
"We're specifically interested in anyone who may have been traveling north or south on Buck Road that may have observed someone suspiciously in the area or a vehicle. Anything that they feel might benefit us," Police Chief Barry Pilla said.
A $10,000 reward is being offered for help in the capture and conviction of the suspect.