The victim had just left a dress shop in Feasterville with her 16-year-old daughter, NBC News said.
The two were sitting in a car in the parking lot Thursday night when Kenneth Philipp pulled up behind them.
Philipp fired three shotgun blasts into the vehicle, The Philadelphia Inquirer reported.
The teenager's hand was injured by broken glass, and her mother later died, NBC reported.
Philipp fled the scene, but police tracked him to a nearby intersection a few miles away.
Authorities said Philipp, 50, got out of the car and started firing at the officers, who fired back, NBC News reported.
One officer's shot and killed Philipp, the Inquirer reported.
Philipp was released from jail in February. He had been held for assaulting his ex-wife with a knife, police said.