AFTER STARTING THE VEHICLE IN MY GARAGE, I NEEDED TO GO BACK INTO THE HOUSE TO GET SOMETHING. I SHIFTED THE CAR TO PARK TO EXIT THE VEHICLE, THE VEHICLE WAS STILL RUNNING. WHEN I EXITED THE VEHICLE THE CAR PROCEEDED TO ROLL BACKWARDS OUT OF THE GARAGE. THE GARAGE IS ON LEVEL GROUND. I ATTEMPTED TO GET BACK INTO THE CAR TO PRESS THE BRAKE. I WAS UNSUCCESSFUL, AND WAS DRAGGED OUT OF THE GARAGE. AFTER BEING DRAGGED THROUGH THE GARAGE I ENDED UP PARTIALLY UNDER THE CAR, I LET GO OF THE CAR AND ROLLED AWAY NOT TO BE RAN OVER BY THE STILL MOVING CAR. I THEN GOT UP AND RAN AFTER THE CAR THAT WAS GOING DOWN MY DECLINE DRIVEWAY. WHEN I GOT INTO THE MOVING CAR I APPLIED THE BRAKE AND SHIFTED THE CAR FROM "DRIVE" TO "PARK". THERE WAS SIGNIFICANT DAMAGE DONE TO THE DRIVERS SIDE OF THE CAR. THE GARAGE DOOR/FRAME WAS DAMAGED AS WELL. I HAD INJURIES THAT REQUIRED AN AMBULANCE.