It happened on North Street in Philadelphia's West Oak Lane section early Sunday morning.
Investigators say it apparently never crossed the thief's mind that his victim just might be armed.
Police say it was the man's third robbery of the night. He forced the victim up against a vehicle along the street and demanded money. That's when shots rang out - but not from the alleged robber.
"'POW, POW, POW.' Real loud gunshots."
Aaron Wisher was listening to the radio in his West Oak Lane home just after midnight when he heard a man on his cell phone quickly followed by seven or eight gunshots.
Wisher tells Action News, "After that I heard somebody yelling. Like, you know, just like talkin' trash. Like, 'Yeah, somethin', somethin', he got 'em, he got 'em. And I peeked out my window and saw somebody laying in the street."
He called 9-1-1 and police responded to investigate. As it turns out, the man who was being robbed had a license to carry a firearm, and shot the alleged robber.
Police say at this time no charges are expected to be filed.