Since they are on the rear, let's bring up the "burnout" or Brake Torquing as another reason there was a ton of heat.
Also possible was the shoes were too tight against the drum and were dragging creating the heat.
Another common problem with rear shoes is the parking brake being adjusted too tight or rusted and sticking holding pressure on the shoes all the time..
If it were my car I would immediate replace them, I have seen a few shoes like these fracture and chunks lock up the wheel.