Jim Jones was a well-known churchman who started the "Peoples Temple" in the 1950s.
He preached against racism, and convinced many members of his congregation move with him to the South American nation of Guyana, where he promised to build a "socialist utopia."
In 1978, Jones lead hundreds of his followers in a mass murder-suicide.
Some of them willingly ingested a poison-laced punch, while others were forced to drink the deadly punch at gunpoint.
The final death toll that day was 909.
And now, 40 years later, Josh Mankiewicz from Dateline NBC sits down with Mark Thompson to talk about that historic day.
This Friday, Josh Mankiewicz and Dateline NBC will revisit the story of the Jonestown mass suicide, 40 years later.