yeah, that was a nitrous
explosion, I can't believe the guy would lean over the motor when someone was trying to crank it.. at least not when your tuning and everything.
I saw that happen with a mustang at the track, cylinoid was bad, filled up the upper intake with nitrous and blew both of the freeze plugs out when he turned the car over, he made it all the way to boom.
I guess the more nitrous that leaks the worse the explosion, the one I witnessed just hosed the guys freeze plugs and TB. he had spares on hand