In an extended preview clip of Oxygen’s upcoming series “Unspeakable Crime: The Killing of Jessica Chambers,” residents of the tiny Mississippi town where 19-year-old Jessica Chambers was burned alive talk about their shock and grief at the horrific crime that claimed the life of a former cheerleader whose “smile would light up a room.”

Four years after the brutal 2014 murder, Jessica’s grieving family members and her friends and neighbors in Courtland still struggle with questions about the unsolved killing that changed so many lives in an instant; and tore apart a quiet, sleepy town when the online obsession with Jessica’s murder turned longtime neighbors against each other.

“Everyone wants to know: Who did this to her? And why?” a friend of Jessica’s says in the preview clip.

“Her life was taken from her in the blink of an eye,” says another friend.

In a heartbreaking scene, Jessica’s mother talks about her last conversation with her daughter before volunteer firefighters found the teen girl, clinging to life, her body almost completely covered in burns after her killer is believed to have doused her car — and maybe her body — with gasoline before setting Jessica and the car on fire.

Traumatized first responders also share their stories of feeling helpless to save Jessica, who was pronounced dead shortly after she was rushed to a hospital on that December night. But she stayed alive long enough to answer the question: “Who did this to you?”

“She said, ‘Eric did this,'” the volunteer firefighter who found her says in the preview clip.

As “Unspeakable Crime: The Killing of Jessica Chambers” will show, Jessica’s last words may have been what kept a jury from coming to a decision at the first murder trial of Quinton Tellis, the man who now stands accused of murdering Jessica just a few weeks after the two first met. His first murder trial ended in a mistrial because the jury deadlocked.

The Oxygen documentary series premieres on Saturday, September 15, just ahead of Tellis’ retrial in Batesville, Mississippi.

Stay with CrimeOnline for complete coverage of the murder trial and “Unspeakable Crime: The Killing of Jessica Chambers,” which will air on Oxygen on Saturday nights at 7 p.m.