The shooting happened at 10:34 p.m. on Tuesday outside a Chinese food store at 6600 North 18th Street in the West Oak Lane section.
Police say the gunman walked up to the front door and fired a shot at the victims.
Surveillance video from inside the store shows the victims struggling to keep the door closed as the gunman tries to force his way inside while brandishing his weapon.
After struggling for a few moments, another surveillance camera - placed outside the store - shows the man back up and fire several shots through the glass door, hitting the victims inside.
The gunman then fled north on 18th Street from 66th Avenue.
The three victims suffered non-life-threatening injuries.
The suspect is described as a black male standing 6'0" to 6'2" tall. He has a medium build, a beard or goatee, and was wearing a dark-colored sweatshirt that may have had a Nike logo on the front. He was also wearing dark-colored pants and baseball batting gloves.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through phillypolice.com.