I agree. It's possible the starter has suddenly gone south, but that doesn't explain the sudden stop. Try a long pry bar in the flywheel teeth, and turn the engine backwards to its normal rotation. If a bearing has "overlapped", sometimes that will free it up enough to crank it with the starter. It sounds like you're going to have to drop the pan and inspect things in any case. Hope the damage isn't too bad!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!