On the night of Dec. 6, 2014, firefighters responding to a call about a car fire along a rural Mississippi road encountered a horrific scene: A teenager who was engulfed in flames was walking toward them, clothed only in her underwear. Her burning Kia Rio was parked nearby.

“Help me, help me,” she cried, as a firefighter wrapped her blistered body in a blanket and laid her down.

The teen was later identified as Jessica Chambers, a 19-year-old former cheerleader. She had been lit on fire with a flammable liquid, causing covering 93 percent of her body, and would die after being airlifted to a hospital in Memphis.

Before she died, paramedics asked who did this to her. Though it was difficult for Chambers to speak, she shispered a man’s name that sounded either like “Eric” or “Derrick.”

Her tragic death garnered national attention, drew online sleuths to a “Justice for Jessica” Facebook page, spawned a $50,000 reward for information leading to an arrest and a large-scale manhunt for her killer.

The mystery surrounding the murder is the subject of Monday’s episode of People Magazine Investigates. Titled “Burned Alive,” the episode airs Monday at 8 p.m. ET on Investigation Discovery. (An exclusive clip is shown above.)

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“What could a [small] 19-year-old girl do to make you burn somebody alive?” Jessica’s father Ben Chambers previously told PEOPLE. “This is beyond murder. This is revengeful, hateful killing.”

At the time of her death, police had precious few clues.

Ninety minutes before she was found, Chambers was captured on grainy footage from gas station surveillance cameras about one mile away. Chambers was walking toward the station in the footage, which showed her waving before walking over to speak with someone.

The surveillance camera also picked up a man wearing a striped shirt filling up a gas can before walking in the same direction as the teen. Soon after, Chambers returned to her car and drove off.

But the mystery lingered: Where did Chambers drive, and how did she meet such a brutal fate?

People Magazine Investigates: Burned Alive airs Monday, Feb. 18 at 8 p.m. ET on Investigation Discovery.