Burbank police said the boy, whose name was not released, knocked on the front door of a 67-year-old woman whose grandson beat up one of the boy's friends at school, the Burbank Leader reported Tuesday.
Lt. John Dilibert said the boy yelled "you suck" at the woman and pointed the toy gun at her before fleeing.
Dilibert said the toy gun appeared to be an Airsoft gun, a realistic-looking toy that shoots pellets, CBS News reported.
"They're replicas," Dilibert said. "They look just like the real thing. It shoots soft pellets, like a BB gun."
The boy was arrested on suspicion of brandishing a weapon and released to his parents. He was given a citation and will have to appear in court, Dilibert said.