Unless that was the last round loaded, I'm not sure I would have been turning that thing toward me to take a look into the revolvers chambers where that barrel used to be! He's lucky to still be in one piece.
It may be a result of the slow motion vs real time, but it sure looked like there was a whole lot of flame out of the wrong places (e.g., hammer side of cylinder) on the round that blew the barrel off. Thoughts: Faulty brass, way overloaded, cylinder not in alignment.
I've seen a barrel blow of a revolver and the top strap/cylinder come apart. Both times they were caused by overpressure due to custom reloads - to much powder, brass used to many times, wrong powder, wrong primer, to heavy a bullet. The guy's lucky that he's just out a gun that might be repairable.