The meth must have kicked in.

OH MY FUCKIN GOD WHAT A DRUGGED OUT LOSER

First I thought the same thing as you, drug addict fall, but analyzing the video, falling to tread water bottle cap.

who was it?

i think that may have been mayhem fest.

He might have blacked out or browned out from howling/screaming for too long thereby depriving his brain of oxygen. Its a long way to the top if you want to Rock and Roll.

Thankgod he got hurt