And in the process turns the wooden Bolly 28x10 into matchsticks and sprays the debris up to 30m away!

I've read a whole bunch on several forums where prop bolt failure is often the root cause of throwing props. The thing here is I don't see how throwing the prop would make the engine stop dead still from 6k+ rpm instantly. I think the sudden stop is what caused the prop to shatter and depart, tearing off all the bolts in the process. But that would point to detonation or maybe pre-ignition.
Ofcourse the crank was bent after that but was not obvious until the crank case bolts were released and the engine turned over showing a wobble between the front / back case interface.

I'd love to hear any thoughts on this one. Especially any experience with motors stopping dead still. Scared the crap out of me I can tell you!

Norm.