The Heaven's Gate UFO cult was started by Marshall Applewhite and Bonnie Nettles in the USA in the early 70's. Both had a history of studying biblical prophecy, past-lives, UFO's and other fringe beliefs. They garnered a group of followers and in 1975 the group sold all their possessions and seemingly 'disappeared' - in reality they simply travelled around the country as vagrants.
The group grew and by the 1990's had purchased a large ranch in California, where they had a 'revelation' about comet Hale-Bopp which would be visible in 1996 - 1998. The group held to the idea that there was a spacecraft trailing the comet which was coming to resurrect them.
Applewhite persuaded 38 followers to commit suicide so that their souls could board the supposed craft.Over three days in March 1997, Applewhite and 38 followers killed themselves in expectation that their spiritual souls would be taken to another "level of existence above human". We are unable to confirm if this is true.