Investigators said the male employee who fired the gun claims it was an accident. The incident happened just before 5 p.m. Sunday at the Smoke Shack #2 on East Avenue J in Lancaster.
According to detectives, the storeowner was in the front and the victim, who worked part-time at the shop, was in a back area where a shotgun was kept.
"Another employee decided to go back to where she was. She was in the area back there cleaning up. And at this point, he said the shotgun discharged. We're not sure if it's accidental or intentional," said Lt. Eddie Hernandez with the Los Angeles County Sheriff's Department.
Investigators said the male employee told them he moved the gun and it went off, hitting the victim once in the chest.
She was rushed to the hospital, where she was pronounced dead. Friends of the victim said she has a 6-month-old baby.
According to a family member of one employee, the store has been robbed several times and the owner had the shotgun for protection. There are security cameras in the store, but the shooting was not caught on camera.