CAR PARKED, RUNNING, DOOR OPEN TO CHECK MAILBOX. 15 FEET AWAY, CAR STARTED TO ROLL BACK, WENT TO STOP WITH RT LEG REACHING BRAKE. COULDN'T REACH BRAKE, PUSHED ON OPEN DOOR, CAR DID NOT STOP. I FELL BACKWARDS AS LEFT LEG HOPPED AND COULD NOT KEEP UP. ON GROUND TRIED TO BRACE CAR WITH LEFT LEG, RIGHT AND LEFT LEGS WENT OVER HEAD UNDER OPEN DOOR AS CAR CONTINUED TO ROLL IN GEAR BACKWARDS. CAR WAS NOT ON INCLINE. WENT AFTER CAR AND HAMSTRINGS AND CALVES SNAPPED AND FACE PLANTED. ATTEMPTED TO RUN AFTER CAR AGAIN WITH SAME RESULT. SEVERE MUSCLE INJURY TO BOTH LEGS. NOW HIP IS DISLOCATING, MRI PENDING. CAR ROLLED ACROSS STREET AND WAS TRAPPED INTO TREES.