The deceased was identified by police as Lamar Allen, 25, of Toledo.
The incident occurred about 9:45 a.m. at the Express Carryout, 1920 Mulberry St.
The two adult male suspects were in the process of emptying the store's cash register when the clerk fatally shot one of them, said Toledo police Sgt. Joe Heffernan. The victim, who was struck multiple times, collapsed right in front of the counter.
It was unclear whether the second suspect, who fled the store, was hit by a bullet or got away with any cash. He was last seen running toward Stickney Avenue.
The robbery attempt happened about 9:45 a.m. and just as the store had opened for the morning.
The clerk, whose name police withheld, was working by himself at the time.
The robbery attempt was caught on a store video camera. Forensic experts are reviewing the tapes.