PARKED AND SHUT OFF, DISCONNECTED TRAILER. TRUCK ROLLED BACK WHILE IN PARK. I JUMPED OUT OF WAY AND TRIED TO OPEN DOOR TO STOP. DOOR KNOCKED ME DOWN AND CONTINUED BACKWARDS DRAGGING ME. FINAL STOP OVER EDGE OF POND AGAINST TREE STUMP. HAD TOWED TO DEALER FOR INSPECTION BY CHEVY ENGINEER. 2 WEEKS NO COMMUNICATION.