RCMP say the incident began when the 61-year-old was attempting to park his pickup truck in his driveway on Lakeview Crescent near the intersection of Broadway Avenue South.
Thinking he had put it in gear, the man started to get out, but the vehicle started rolling away. He tried to jump back into the truck, but he fell to the ground instead and was pulled underneath and run over by the vehicle.
It continued rolling down Lakeview Cresent until it struck a parked Honda Civic and then tumbled over the retaining wall above a McDonald's parking lot, and landed on a pickup truck parked with two people inside.
That couple in the pickup suffered minor injuries. The owner of the runaway truck was taken to hospital in critical condition.