The victim's coworkers tell Action News he is in stable condition.
The shooting happened just after 7 p.m. on the 5400 block of Eadom Street.
Neighbors said the victim lives across the street and has worked at the storage business for years.
Walt Sweeten, who lives next door to the victim, said he arrived home to find first responders rushing his neighbor to the hospital.
"I said to him, 'Are you okay?' He said, 'I'm shot,'" Sweeten said.
Police said the employee was inside the facility with a customer when a man wearing a face mask and rubber gloves pulled out a gun, ordered both people to get on their knees, and demanded money from the register.
Investigators said the victim complied and handed over cash, but the suspect opened fire anyway, hitting the employee in the shoulder and chest. The customer was not injured.
The suspect fled on an electric mini-bike, police said.
"I hope they find him. I really do. I hope they find him," Sweeten said.
The incident was captured on the facility's surveillance cameras, according to police. The owner declined to release the footage to Action News, but investigators are reviewing it.
Neighbors described the victim as a wellliked and trusted presence in the community.
"He's one of the guys that's like one of the pillars in the neighborhood, so for that to happen to him is unfortunate," said neighbor Kwame Palmer. "He looks out for everybody around here. Anything that we need, we can go ask him about the neighborhood; he's always been a standup guy."
Police have not said how much money was taken. Investigators believe the suspect was targeting cash and not any of the storage units.
The Philadelphia Police Department is asking anyone with information to call its tip line at 215686TIPS (8477). Tipsters may remain anonymous.