I haven't heard of this one.. but I am pretty sure this is a staged tape. If this were real, its totally criminal and I would doubt people are dumb enough to make copies of it and sell them.

I have heard of something close to what you saw that deals with homeless people kicking the $^%# of each other for money. They would get the homeless drunk and have them fight. The people who taped this and sold their tapes later got in trouble and went to court. I don't remember what happened in court but there was a penalty nonetheless.