The two were sitting inside a car while their mother was shopping at the store in Choctaw when the older brother found a gun and inadvertently shot his sibling around 2 p.m., Choctaw Police Chief Kelly Marshall told The New York Post.

Bystanders heard the shot and called 911.

Two police officers arrived on scene and applied two chest seals to the boy’s entry and exit wounds to stop any bleeding, Marshall told the newspaper.

He was initially going to be airlifted to a hospital but responders decided to take him to the University of Oklahoma trauma center by ambulance, according to the chief.

His condition is believed to be stable and he is currently awaiting potential surgery, Marshall said.

Police have started investigating the incident.