Kitsap County Sheriff's Office spokesman Scott Wilson said Tyler James Wade died Oct. 19, the Kitsap Sun reported Tuesday.
The boy was taken to a hospital in Tacoma after friends found him hanging from a tree by a scarf outside a Kitsap home Oct. 16, the newspaper said.
Investigators said he had been playing with friends, who had gone inside before the incident. When they returned outside, they found Tyler entangled in the scarf.
"The youngster appears to have been engaged in trying to stage a prank," Wilson said. "It was an unintended accident."
The principal of Tyler's school, who said he'd known the boy for years, described him as having "an engaging, creative" personality.
"He was a little bit of a jokester," Sidney Glen Elementary Principal Jason Shdo said. "He was very affectionate, with a soft heart."