We've seen it happen and it's actually kind of funny. It sounds really bad and when the driver turns the key off and pulls the key out it still runs and sounds horrible. Then they hop out of the car and pull the coil wire out and invariably get an arm numbing shock in the process. That stops the engine but the starter is still cranking. Finally, they pull a battery cable off and then, when their senses come back to them, the say
"well wtf just happened and why?"