BUCKINGHAM TOWNSHIP, Pa. (CBS) — June 1977. A father and son made a gruesome discovery in some woods in an area of Buckingham Township, Bucks County, known as Church Hill.

The mutilated body of Shaun Eileen Ritterson was located in some brush. She was 20 years old from Croydon. To this day, her killing remains unsolved.

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Her death stands out as one of the most brutal in county history.

“She was eviscerated. She was clearly murdered,” Bucks County District Attorney Matt Weintraub said. “I’m not sure if she was strangled or not first. But she was eviscerated.”

Weintraub revived the investigation several years ago, reviewing old notes and details that for decades sat in a box on a shelf. Detectives have long had a theory on who killed Ritterson.

“We were vectoring in on our prime suspect, Shaun’s Ritterson’s uncle, he died,” Weintraub said. “Unfortunately, we exhausted all leads at that time. We had no more credible suspects.”

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It’s believed the pair had an argument. In published reports before his death, Ritterson’s uncle denied involvement but reportedly declined to cooperate with investigators.

“My theory is Shaun was close with her uncle and they had a disagreement about some intimate things,” Weintraub said. “That disagreement turned fatal. A terrible way to die, ungodly way to be left, it’s not right, fair, it’s unjustified. Nobody should have to suffer like that.”

The case recently made the news when the DA’s office returned a ring to Ritterson’s surviving family members.

“She asked me point blank, hey I know you have this ring, it’s a love ring that Shaun used to wear, and would you be able to give it back to me so I can share it with my family?” Weintraub said.

Prosecutors are convinced somebody knows something about the brutal killing of Shaun Eileen Ritterson.

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“If anybody in the public has any information about this age-old murder, we would love to know it, let us be the judge of the value of that information,” Weintraub said.