CAR JUST PARKED IN PARKING SPOT AND PASSENGER TOOK SEATBELT OFF AND STARTED TO PULL DOOR LEVER. PASSENGER HEADREST AIRBAG BURSTED OPEN, KNOCKING THE PASSENGER HEAD FORWARD. HEADREST MADE A LOUD BANG. THE MOTION AND FORCE OF THE HEADREST BANGED AGAINST THE BACK OF PASSENGER HEAD CAUSING INSTANT HEADACHE AND WHIPLASH.