This usually happens when a car without a cat is running too rich (too much fuel not enough air, if the cat is there and working properly, it would burn the fuel that was unburnt in the engine but would quickly become clogged.) The unburnt fuel would soak into the packing of the muffler, and when it gets hot enough, boom. This doesn’t, however, doesnt explain why the car to stop running. There may be multiple issues.