It’s probably a Satanic ritual, but what he described seeing in that video is also parasite spreading behaviour. Exposing yourself to blood is a clear way to catch blood borne parasites. Blood from a corpse is more riddled with parasites because there is no longer a functioning immune system to suppress them. Parasites cause all kinds of organisms to take on bizarre and disgusting behaviours that help them spread. That’s what this looks like. Those people were probably infested.