My parents went to start the Volt last night but the battery was completely dead and there were no interior lights or power of any kind. SO they called onstar. Onstar had someone roll the car out of the garage to tow it back to Sport Chevrolet. But after the car was taken out of the garage the floor of the garage was completely melted and burnt with huge holes in the floor where the Volt was. Any idea what can cause this this? Pictures attached. The garage is designed to contain very high heat and there was nothing flammable anywhere in the garage.