I WAS DRIVING AND THERE WAS THE SMELL OF BURNING ELECTRONICS AND MY TRUCK CABIN FILLED WITH SMOKE. I PULLED OVER, AND SAW THE DEFROSTER ON THE REAR WINDOW WAS SMOKING. I EXITED THE VEHICLE, OPENED MY DOORS TO LET THE SMOKE OUT, AND ALL OF A SUDDEN I HEARD AN EXPLOSION LIKE A GUN SHOT AND THE REAR GLASS GLASS SHATTERED.