Upon completion of his delivery at a customer's location, a driver returned to the truck, placed his feet on the driver's side step, reached into the cab and turned off the power take off. The truck began to roll. The driver tried to enter the cab to apply the brakes, but just before being able to stop the truck, the right front wheel exited the pavement causing the truck to roll onto its right side. The driver went over the truck landing onto the driveway below. The vehicle continued to roll over, crushing the left side on a rock. The truck came to rest with the damaged step straddling the driver's right leg, fracturing his right ankle.