The Heavens Gate Cult Documentary Trailer.

Cult of cults convinced people they were aliens destined to transcend their bodies. Tried to castrate each other, but it went so wrong that one man had to be rushed to hospital after bleeding out. They thought in the tail of a comet was a spacesip which would take them up into an alien spaceship and make them immortal. All took poison and killed themselves - this is heaven's gate.