It happened at 19th and York Streets at 3:30 a.m. Thursday.
Police say surveillance video showed the victim hanging out in front of the store and getting into a verbal dispute with someone else.
About 10 minutes later, the footage shows a masked man walking from behind the store, up to the victim and firing a shot from a few feet away.
The gunman turned around and fled west on 19th Street.
The victim is in the hospital in stable condition with three gunshot wounds.