Does anyone remember what this event was?

I remember reading in my school library about 3 years ago about this real evil kind of magcian/hynotiser guy who did this thing about 10-50 years ago where he hypnotised thousands of people in a desert kind of place and told them all in their trance to kill themselves. I don't know if he's still alive but this is definately true becasue I read about it in a fact book about magic and hypnosis. I think the story is related to the word black. Maybe this happend in a Black Desert or his surname was black or I don't know. Does anyome remeber something like this happening? I think it happened in America or Eygyt or Saudi Arabia or something. Sorry this is a bit vague but it's all I can remember!