PLYMOUTH, Minn. (AP) — Police say a 7-year-old boy fatally shot himself in his suburban Minneapolis home after a loaded handgun was found in a box containing a toy.

Police were called to a townhome apartment complex in Plymouth around 3 p.m. Wednesday on a report of a child bleeding from the head. When officers arrived they discovered Keyaris Samuels with a gunshot wound.

Police said Thursday that the boy and three other children were without adult supervision when the gun was discovered in a box containing a hoverboard. The other children were outside when Keyaris accidentally shot himself. The boy’s mother came home shortly afterward.

Plymouth Police Chief Michael Goldstein says the boy’s mother told police she doesn’t know the source of the gun. Police are investigating and want to hold the gun owner responsible.