One masked man served as a lookout as another shot a convenience store clerk, Philadelphia Police said.
The men entered the 7-Eleven store at Torresdale Avenue and Disston Street in the Tacony neighborhood just after 4 a.m. Tuesday.
As one man stood by the door, the other robbed the two workers -- the only people in the store at the time.
"Dressed all in black -- a black hoodie, black pants -- and he had a half mask on his face... and he had a gun," Capt. George Fuchs said.
A 53-year-old employee emptied one register, police said.
"He did cooperate, give them all the money from that register," Fuchs said.
But when he couldn’t open the second register, the robber became angry and shot the employee in the shoulder, Fuchs said.
Doctors at Aria Torresdale Hospital listed the store clerk in stable condition, investigators said.
Both suspects ran off on foot. Police captured a man on a nearby rooftop a short time later and called him a person of interest.
The shooter remained at large Tuesday morning. Investigators hoped surveillance video could help identify the shooter, who had his face only partially covered.
The store reopened once police wrapped up their investigation on the scene Tuesday morning.