I was trying to defrost my windows and my air was on so I clicked the air off so the heat could come on and I started smelling a matalicky smell. I drove to a stop light and when I stopped the back windshield popped and then shattered. I then went to drive again to take the car home and I started to see smoke. Once the light changed I continued to drive to get the car home I happened to look through the rear view mirror and saw fire in the trunk , once I saw the fire I pulled over on a street and stopped the car and then all the sirens in the car started going off so I turned the car off got out and called 911.