Police say around 11:33 p.m. PT the truck was travelling down Boundary Road with three people in the cab when the victim fell out of the box. He died at the scene from his injuries.
Police are still investigating the cause of the incident, but RCMP Sgt. Robbie Drake said the road was straight, the truck did not appear to have left the road and there were no other vehicles involved.
The driver is scheduled to appear in Chilliwack Provincial Court this afternoon to face a charge of dangerous operation of a motor vehicle causing death.
The names of the driver and the victim have not been released by police, but police did say everyone in the truck at the time was from Chilliwack.