ok, so just changed out the tube since this last one had just happened. I don't think it was the exhaust since it happened when the car was turned off. It was definitely a "bang" when it popped. I checked the tube and it looked more like a pin hole than a blowout or pinch flat. I checked the tire and only thing I could find is a similar size hole/tear in the sidewall but does not look to go all the way through the tire.

So the mystery continues...