Vehicle was parked on a slight incline with transmission in Park and electronic parking brake engaged. Engine was running. While unloading groceries, driver leaned into vehicle and pressed the engine start/stop button to turn the vehicle off. Immediately after engine shutoff, the vehicle began rolling backward. Driver attempted to re-engage Park and electronic parking brake multiple times without effect. Vehicle continued rolling for approximately 20â30 seconds before stopping. Driverâs foot was run over by the vehicle, resulting in injury. No warning messages were observed prior to the incident. Cause unknown. Vehicle remains available for inspection.