Clayton Everley was digging a hole in a small sand pile next to his home when the sand collapsed, burying his head, arms and shoulders, Kittitas County Sheriff's deputies said.
Clayton's parents found him, started CPR and called 911. His father even had an automated electronic defibrillator in his work vehicle but was unable to revive him.
The boy was rushed to the Kittitas Valley Hospital, then eventually flown to Children's Hospital in Seattle but died from his injuries Thursday evening, deputies said.
Police are still investigating the incident.