Sounds like a bunch of rumors concerning several people combined into one, though I could be wrong. Dead (what a telling nom de plume) was obsessed with death. Dude had a thing for hoarding dead birds and burying his clothes to 'give them that grave scent'. He also loved cutting himself on stage to the point at least several shows had to be stopped just so his bandmates could call an ambulance and bring him back from the brink. It may or may not be surprising that the guy blew his head off with a shotgun at the hearty age of 22. He was weird even by black metal standards and that's according to the people who knew him and played music with him.
As far as screams go, Abruptum were rumored to have cut themselves prior to recording sessions but iirc nothing was proven.
And there is Nattramn, a real basket case who was allegedly institutionalized after trying to kill a child with an axe or something along those lines.
Black metal is one of those few genres where at least some of the appeal comes from aspects not related to music itself and it can foster some unhinged individuals. You don't really see this in other subgenres of metal, certainly not to the same extent. One could say it's unique for what it's worth.