Four decades after over 900 followers of Jim Jones committed suicide at Jonestown, survivor Tracy Parks recounts her escape from the horrors of the group's compound in the Guyana rainforest

Nearly four decades have passed since that afternoon Tracy Parks knelt on the rain-soaked, muddy airstrip in Guyana, cradling her mother’s lifeless body in her hands, shaking her in a desperate attempt to wake her up.

But for Parks, it feels like it happened just yesterday.

Get push notifications with news, features and more.

The explosion of gunfire had stopped, but all around her lay bullet-ridden bodies — some dead, others bleeding and moaning. “Get in the jungle,” her father Jerry screamed. “Run.”

Tracy, then 12, looked up to see her older sister Brenda sprinting across the airport runway toward the dark wall of trees. Before she knew it, she was running right behind her, racing toward the dense rainforest.

“I felt like I wasn’t in my body,” Tracy recalls in the new series People Magazine Investigates: Cults, airing Monday, June 11 at 9 p.m. ET on Investigation Discovery. “We were so scared, we just kept running.”

Image zoom Tracy Parks Jonathan Sprague/Redux

After the fever-ridden, nearly unconscious girls staggered out of the jungle three days later, they became fully aware of the unimaginable horror they’d escaped: More than 900 members of the Peoples Temple religious sect — the group that she and her family were attempting to flee when they were ambushed — had committed mass suicide by drinking cyanide-laced grape punch. Among the dead were 304 children whose parents forced cyanide-filled syringes into the mouths of those too young to sip from cups.

Their bodies, along with that of the cult’s leader, Jim Jones, now lay rotting seven miles away in the blistering equatorial heat at the group’s compound, known as Jonestown.

• For more on how Tracy Parks escaped Jonestown, subscribe now to PEOPLE or pick up this week’s issue, on newsstands now.

Image zoom Kayt Jones

“My brother broke the news to me little by little as the doctors were nursing me back,” Parks, who lost five family members in the massacre, tells PEOPLE in this week’s issue. “‘No one is alive,’ he told me. They’re all gone.'”

Today, 40 years later, Parks — one of the youngest Peoples Temple members to escape the largest mass suicide in modern history — still struggles to cope with the trauma.

It was the scandal that rocked America’s most storied political family and changed the course of presidential history. PEOPLE‘s first-ever podcast, Cover-Up, dives into the Chappaquiddick scandal and attempts to piece together what happened in the hours after Ted Kennedy’s car went over a narrow wooden bridge, killing his passenger, Mary Jo Kopechne. Subscribe now on Apple Podcasts, Spotify, Google Play or wherever podcasts are available.

Image zoom Tracy Parks in a Guyana hotel with her father, Jerry Ken Hawkins/AP/Rex/Shutterstock

“This wasn’t suicide,” insists Parks, 51, now a California day care owner. “This was murder. Those children didn’t want to die and neither did many of the adults.”