The Philadelphia Police Department said the incident happened just after 4 p.m. at a Metro PCS store in the southwest part of the city when an unidentified man who appeared to be in his late 30s entered the business.
The man was trying to rob the store when the lone employee inside – who has a permit to carry a firearm – fired at the would-be robber multiple times, striking him.
"I heard about 10 shots and I got out (of) the car to look around and I saw the guy that works there run out of the store with a gun in his hand," a man who wished to not be identified told FOX29.
Police said the robber was pronounced dead at the scene minutes later.
Debra Earle, who lives nearby, said she was rattled by what happened at the store.
“Very upsetting, very upsetting," she told FOX29. "You can’t feel safe walking down the street paying your phone bill right down the street from your home."
No other injuries were reported and the weapon was recovered, according to police.
The investigation into the incident is ongoing, FOX29 reported.
The Associated Press contributed to this report.