Samuel Thompson's grieving parents have been given confirmation a body found in bush north of Brisbane was their slain son.

Forensic police have completed a post-mortem, finding evidence the 22-year-old Albion man was assaulted before his death.

A police spokesman said it was unclear whether the assault caused his death.

Police believe the man whose abandoned orange Ford Mustang sparked the year's largest murder investigation was likely dead before the car ever turned up at a north Brisbane waterhole that featured extensively in his murder investigation.