The crime happened on January 13 at the Circle C Market on Kings Canyon in Centerville.
Surveillance video shows a man and a woman with a gun going toward the employee, forcing the clerk behind the counter.
The man then ordered the clerk to get down before hitting her on the head.
As the man stole cash from the register, a third suspect walked in.
All three eventually ran from the store before taking off in a car.
Anyone with information is asked to call the Fresno County Sheriff's Office.