Ontario's police watchdog are investigating a fatal collision south of Peterborough on Friday night. According to the Special Investigations Unit, a vehicle fled from a traffic stop being conducted by a Peterborough Police Service officer on County Road 28 in Cavan-Monaghan Township. A short time later the vehicle was involved in a collision. The SIU say a 19-year-old man in one of the vehicles was pronounced deceased at the scene.