Yeah, I must admit I've had more than my fair share of stack fires. Judging by the amount of actual flamage, I'd guess it's an injector failure. You stated on RME (if I'm remembering right), that they couldn't get it to shut down. That might also indicate a mechanical failure such as a broken piston. Once that kind of failure occurs, the engine will continue running even with the fuel shut off. How is that possible you ask??? The crankcase oil is getting forced into the breather due to the mechanical failure. Although they'll run poorly, diesels will run on just plain motor oil, at least till the crankcase is empty. The only real way to kill an engine in that situation is to cut the air off to it, or overload it to stall it out. I run butterfly valves on my intake systems for just such an occurance.