Police say 23-year-old Rita Pultro was taken into custody Sunday afternoon.
"She was arrested around 12:30 somewhere in the 15th district. She did try to flee, ran into a house and was arrested," said Commissioner Joseph Bail, Chester Police.
Pultro was the second piece of the puzzle as police investigated the shooting death of Jason McClay.
Only Action News was there Saturday when the first suspect - 24-year-old David Wiggins was arrested in the Grays Ferry section of the city.
Police say the duo was seen on surveillance video entering the Rite Aid at 9th and Highland streets in Chester, just before closing Thursday night.
McClay, a store manager, was shot and killed.
Police say they are still investigating what the relationship is between the two suspects and who pulled the trigger.
Authorities believe the motive Thursday night was robbery.
"Anytime we're able to wrap up a homicide is a tremendous relief," said Commissioner Bail.
McClay's family gathered Saturday for a candlelight vigil remembering the Navy vet who loved sports.
After hearing of the first arrest they expressed gratitude to the Chester Police Department and never doubted that Pultro's arrest would come soon.
"The Chester cops told me it would take a day and a half and he kept his word," said Pat Reiley, McClay's brother.
Authorities say good police work and fingerprints left at the scene led them to quickly identify the suspects.
Both Wiggins and Pultro face first, second and third degree homicide charges and related offenses.