The Cincinnati Enquirer (http://cin.ci/Vu93Up ) reports it happened early Monday at a Sunoco station north of the city.
The workers, who haven't been identified, said the robber came in at around 12:30 a.m., pointed a gun at them and demanded money.
The clerks told police the suspect — believed to be in his teens — had already come around the counter and taken cash when they fired a handgun and shotgun at him in self-defense.
The names of the clerks haven't been released. No charges have been filed, but police say their will consult the county prosecutor's office.