Ever hear of an engine conking out while cranking?

[Tougemonster]

I just had used motor seize on start up. It turned and fired normally, almost reached idle speed, then clunked pretty violent like. I'm tearing it down soon to see what happened. Thought it was carbon locked,still might be. I did break a 1/2 breaker bar trying to free it up though. Now i have swellbo, I thought N/A's weren't suppose to break this much