The clerk described the boy as only up to her chin, but she believed the BB gun was a loaded handgun.
The boys then went to a Subway restaurant across the street, where they are accused of executing a similar plan.
According to North Las Vegas police, the 11-year-old boy was brazen enough to hold his BB gun to an employee's head at Subway.
The 11-year-old boy's mother didn't apologize for her son's actions, but she did acknowledge that her son and his 12-year-old partner deserved punishment.
Police said this wasn't the first time the 11-year-old committed such a crime. Investigators alleged that police were able to track him down because of his prior felony charge.