Officials from the Mason County Sheriff's Office say the boy was inside a home in a residential area on the reservation when he was shot in the chest with a rifle at about 7:15 p.m.
According to the Sheriff's Office, the victim and a 13-year-old boy were playing with guns they found inside the residence. After the shooting, the 13-year-old ran to a neighbor's house to call 911.
Police and medics arrived shortly after the shooting and called for an airlift to take the victim to Harborview Medical Center, but the boy died before the chopper arrived, according to deputies.
It's unclear if anyone else was injured in the shooting.
A woman who lives on the same block said everyone in the neighborhood is close. She said the victim and the second boy were friends and had gone fishing together earlier on Tuesday.
Skokomish Police and Mason County Sheriff's deputies are investigating.