It happened just after 5:30 p.m. in the 100 block of Bustleton Pike in Feasterville.
According to authorities, a Northampton woman in her 50s was with her 16-year-old daughter pulling into a dress shop to pick up a prom dress.
The woman had a protection from abuse order against her ex-husband, identified as 50-year-old Kenneth Philipp.
Philipp, however, was recently released from Bucks County Prison and was stalking her with a shotgun.
"The doer pulls in behind, perhaps blocking her, goes to the trunk, gets out the shotgun and then proceeds," Bucks County District Attorney David Heckler said.
The woman was pronounced dead at the scene.
The daughter was taken to St. Mary Medical Center with injuries to her hand.
Police say Kenneth Philipp then fled the scene in his older model Lincoln Town Car.
Phillipp was being followed by a North Hampton police officer in the area of Buck and East Holland Roads, when he suddenly pulled over.
Northampton Township Police Lt. Mike Clark said the suspect then exited the vehicle and began firing at the officer.
Investigators say the officer was able to return fire, striking and killing Philipp, but not before the officer himself was shot in the chest.
Fortunately, he was saved by his bulletproof vest.
Philipp had encounters with Northampton police in the past for trying to break into his ex-wife's house with a knife. He had also been accused of making terroristic threats against police.