California Congressman Leo Ryan went to discover the truth along with an NBC News crew. Steve Sung was the soundman.
"We thought the place would be people scared, frightened. It turned out to be just the opposite," Sung told CBS News correspondent John Blackstone. "I mean it looked like a very well-run community."
But then an elderly woman handed a reporter a note.
"The note said help us to get out of here," Sung recalled.
Others began begging to leave and order quickly turned to chaos.
"All of a sudden, they pick up rifles and start shooting at us," Sung said.
Rep. Ryan lay dead as did NBC reporter Don Harris and cameraman Bob Brown.
"I heard a real loud shot, and piercing pain on my shoulder," Sung said. "I was so scared, I didn't know what to do."
Then Sung said, "I shut my eyes, closed them pretending I was dead and they walked past me."
With armed guards ringing the compound, Jim Jones then ordered everyone - adults and children - to drink a mixture of Kool-Aid laced with cyanide.
"Let's just be done with it. Let's be done with the agony of it," Jones was recorded telling his followers, whom he called to "die with a degree dignity."
The compound soon became stone silent. Bodies piled on top of bodies - over 900 in all.
Such was the scale of the horror at Jonestown that many cemeteries didn't want to accept the dead, didn't want to be associated with the tragedy, reports Blackstone. At the Evergreen Cemetery in Oakland, Calif., 409 victims are buried in a mass grave.
One of the enduring mysteries is how Jones himself died. He did not drink the Kool-Aid. He was shot, but no one, to this day, is sure by whom.
Thirty years later, Sung, who is now a freelance video editor, still carries the physical scars from that day. But while those wounds have healed, the emotional scars remain.
"All the children are gone," Sung said. "I, I just couldn't believe it."