The District Attorney's office says an arrest warrant was issued Friday for 27-year-old Tymeir Henderson.
Authorities say he shot two people on the 700 block of Chain Street in Norristown on Sunday afternoon.
One of the victims, 28-year-old Dyon Thompson, was killed.
Thompson's 19-year-old brother was wounded.
According to investigators, the shooting happened after Thompson had arrived at a home to speak to the mother of his 7-year-old daughter.
That woman is eight months pregnant with a baby boy by Henderson, investigators said.
There appeared to be some kind of discussion, investigators said, then Thompson was shot as he walked back to his car. His brother was wounded as he tried to flee the parked vehicle.
Henderson, a resident of E. Pleasant Street in Philadelphia, is wanted on charges of first-degree murder, aggravated assault and other offenses.
Anyone with information is asked to contact Norristown police or the Montgomery County District Attorney's Office.