I WAS DRIVING THIS MORNING WITH THE TEMPERTURE AROUND 30DEGREES. I TURNED ON MY REAR DEFROST TO THAW MY MIRRORS AND REAR GLASS OF FROST. WITHIN 10 MINUTES OF LEAVING MY DRIVEWAY, WHILE DRIVING I HEARD A LARGE POP THAT RESEMBLED A GUN SHOT, MY DAUGHTER STARTED SCREAMING AND STATED MY BACK WINDOW HAD BROKEN. THERE ARE BURN MARKS ON THE DEFROST CONTACTS, SHARDS OF SAFETY GLASS OFF OF MY WINDOW THAT SHOT OUT WHEN EXPLODED WITH MY 5 YEAR OLD DAUGHTER IN THE REAR SEAT AND HER CAR SEAT. VEHICLE WAS IN MOTION APPROX 55 MPH. THE SOUND ALONE CAUSED ME TO LOCK UP MY BRAKES OUT OF INSTINCT TO INVESTIGATE THE LOUD NOISE THAT SOUNDED LIKE A GUN SHOT AND TO EXAMINE THE VEHICLE. THIS IS A SERIOUS SAFETY ISSUE AND NEEDS TO BE ADDRESSED! THERE WAS A BURNING SMELL OF WHAT SMELT LIKE ELECTRICAL WIRE BURNING PRESENT WHEN THIS HAPPENED AND MINIMAL SMOKE IN THE BACK OF THE VEHICLE.