The fatal shooting occurred after a couple with two children pulled into a service station shortly after midnight, Tacoma Police Department representative Naveed Benjamin said. The woman entered the store to pay for gasoline, and as the man left the car to approach the gas pump, police believe he bumped the seat and exposed a gun.
Benjamin said the boy picked up the gun from the floor of the car and accidentally shot himself. He was transported to a nearby hospital, where he died.
The name of the victim and the others in the car were not released. No one else was injured, police said.
Police said the man had a concealed weapons permit. The type of gun involved was not reported.
Benjamin told Tacoma's KCPQ-TV the case was considered an ongoing investigation.