ACTIVE HEADREST WAS DEPLOYED/ACTIVATED WHILE IDLE AT A RED LIGHT, THE HEADREST HIT THE BACK OF MY HEAD AND MADE ME RELEASE THE BRAKE WHILE STOPPED AT A RED LIGHT, THERE WAS ALSO A VERY LOUD NOISE (KIND OF LIKE A GUN SHOT NOISE). THIS WAS VERY SCARY AS I HAD NO IDEA WHAT HAD HAPPENED OR WHAT HAD HIT MY HEAD, I HAD TO PULL TO THE SIDE OF THE ROAD AND EXAMINE MY CAR TO MAKE SURE IT WAS SAFE TO DRIVE IT. ALL THIS WHILE I WAS IN PAIN RESULTING FROM THE HEADREST HITTING THE BACK OF MY HEAD.