A shopkeeper fought off armed robbers by wrestling one of them to the ground and locking them in the store.
Vijitha Jeyathevan was upstairs when she heard screams and found her brother under attack by the pair armed with a knife and what appeared to be a gun.
Fearing for their lives, she grappled the weapon off one of the robbers while the other fled from Goddard Convenience Store in Hull.
Two 14-year-olds have been arrested and released on bail, police said.
Her brother Thaya Karan was left with minor head injuries after he was hit on the head several times by the robbers.
He described his sister as a "hero" and said her actions had saved him.
After wrestling one of the robbers, the pair managed to trap him in the store until police arrived after the attack on Tuesday afternoon.
Humberside Police said one of the 14-year-olds was arrested at the scene and the second one handed himself in a short time later.
Det Sgt Adrian Dalby said patrols had been stepped up in the area and urged anyone with information to get in touch.