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EXCLUSIVE: Bill Thomas is adamant that in his lifetime, he’ll find out the identity of his sister’s murderer.

In October 1986, the bodies of Cathy Thomas and Rebecca Dowski were discovered inside the 1980 Honda Civic that belonged to Thomas’s sibling. The car had been pushed down an embankment off the Colonial Parkway In Virginia. 

The women were bound with rope and strangled. Cathy’s throat was slit so deep that she was nearly decapitated. Dowski, 21, was found in the backseat of the car while Cathy, 27, was stuffed into the hatchback.

It was the first of several gruesome murders.

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Bill Thomas, a producer on Oxygen's 'Lovers' Lane Murders' is seen here with a portrait of his sister Cathy Thomas.

Bill Thomas, a producer on Oxygen's 'Lovers' Lane Murders' is seen here with a portrait of his sister Cathy Thomas. (Oxygen)

From 1986 to 1989, four double homicides occurred either on or near the scenic, seemingly safe road. All of the victims were young, White, and were either a romantic couple or could resemble one to an outsider. All of the slayings, known as "The Colonial Parkway Murders," are still unsolved.

The cases are now the subject of a new four-part true-crime docu-series on Oxygen titled "Lovers’ Lane Murders." It features LA County Criminal Prosecutor Loni Coombs and former FBI Special Agent Maureen O’Connell who conducted interviews with law enforcement and families, as well as tracked down new leads.

"I hope people will understand that the loss that we’ve suffered has not prevented us as families from continuing to focus on seeing some degree of justice done," Thomas, who serves as one of the show’s producers, told Fox News.

"Yes, this is a tragedy, but hope never dies," he shares. "The families are determined to see this through. We’ve got amazing investigators working on our case. And a lot of fantastic work has gone into the Colonial Parkway murders. We feel like we could be just as close to start to solve these cases."

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Part 1 and 2 of Oxygen's 'Lovers Lane Murders' airs Thursday night.   LA County Criminal Prosecutor Loni Coombs and former FBI Special Agent Maureen O’Connell are seen here speaking with Bill Thomas.

Part 1 and 2 of Oxygen's 'Lovers Lane Murders' airs Thursday night.   LA County Criminal Prosecutor Loni Coombs and former FBI Special Agent Maureen O’Connell are seen here speaking with Bill Thomas. (Oxygen)

Cathy had graduated from the U.S. Naval Academy in 1981 as part of its second class to admit women. She was one of several family members to pursue the Navy.

"I can’t emphasize this enough, but there was a tremendous amount of resistance for those women joining the academy," Thomas explained. "In those first classes at the service academies, they were subject to such levels of hatred and harassment. However, Cathy was unafraid to try things that no one else had done before."

"We told her upfront and we express concern that going to the Naval Academy was going to be very tough," he continued. "But she was undaunted. She was determined… She was also a Russian scholar. She was actually the most improved Russian speaker at the Naval Academy. And remember, this was the 1980s. Speaking Russian was very important because they were, at the time, probably our top adversary in the world."

Despite her drive and determination, Cathy left the Navy just before her death. According to the special, gays and lesbians were banned from the Navy at the time and she had reportedly been investigated by nine agents. However, Cathy moved on and pursued a thriving career as a stockbroker. 

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Cathy Thomas (left) and Rebecca Ann Dowski were dating at the time of their murders.

Cathy Thomas (left) and Rebecca Ann Dowski were dating at the time of their murders. (Oxygen)

"She had been very sorry to leave the Navy after five years, but she didn’t feel that it was welcoming for her as a gay woman," said Thomas. "She discovered after graduating from the Naval Academy that she was a lesbian. So she decided that the Navy wasn’t the right place for her. But she left with great regret because she had hoped to have the kind of career that my dad had."

At the time of her death, Cathy was dating Dowski, a student at the College of William and Mary.  Cathy was eager to introduce her new girlfriend to the family during Thanksgiving that year. Thomas said Cathy was "very upbeat and excited." At the time, she was also thinking about going to grad school and possibly studying international relations.

Thomas said the families were devastated by the sudden, brutal deaths.

"Cathy was somebody that could more than hold her own in any situation," he said. "She had martial arts training from the Naval Academy and she was incredibly athletic. And Becky was also extremely athletic. They were both in top physical condition. [But] we certainly were worried about harassment. Remember, this was over 30 years ago in Virginia, which is a very conservative, military area. So it wasn’t like Cathy and Becky could live their lives in any kind of open fashion."

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The James River as seen from College Creek Beach on the Colonial Parkway.

The James River as seen from College Creek Beach on the Colonial Parkway. (Photo by Scott Neville/ For The Washington Post via Getty Images)

At first, Thomas said his family suspected Cathy and Dowski were victims of a hate crime. However, the string of murders that followed their deaths made them wonder whether a serial killer was involved.

In September 1987, a truck belonging to David Knobling, 20, was found abandoned by the James River Bridge. Three days later, the bodies of Knobling and Robin Edwards, 14, washed ashore on the James River at the Ragged Island Wildlife Refuge. Each had been shot in the head. Multiple reports alleged Edwards had snuck out to meet Knobling before they were killed.

Then in April 1988, Keith Call, 20, and Cassandra Hailey, 18, disappeared after a college party, The Virginian-Pilot reported. The only thing found was Call’s car on the parkway. 

A year later in September 1989, the outlet reported Annamarie Phelps, 18, and Daniel Lauer, 21, vanished from a rest stop in New Kent County. Six weeks later, hunters found their remains. While Phelps was stabbed, Lauer’s body was too decomposed to determine a manner of death.

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The outlet noted that there were no clear signs of robbery or rape for any of these cases.

"It was difficult," Thomas admitted. "When Cathy and Becky were killed, we thought it might be a hate crime. They didn’t use that expression much back then, but that was the idea. And it’s still certainly a possibility. But when the other crimes started taking place, year after year, you’re just shocked… This person may have a law enforcement background or at least understand how law enforcement works."

Thomas described the Colonial Parkway as a popular spot to travel along the river. At night it’s dark and isolated, making it an ideal spot for couples to be romantic discreetly. 

"Some longtime law enforcement people have said to me that it was like the wild West out there at night because it was only patrolled every few hours," said Thomas. "So people knew you could go there and basically be left alone, especially at night."

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Colonial Parkway murder victims

Colonial Parkway murder victims (Oxygen)

Thomas said that over the years, there have been moments where he was frustrated with the investigation of his sister’s murder. He said extremely graphic crime scene photos were leaked to the public, fueling the family’s anguish. However, Thomas claimed new tips come in "every week or two," giving hope that these cold cases can be solved today.

"I’m very optimistic," he said. "In 1986, DNA was barely out of the lab and it wasn’t really used commonly in law enforcement applications. Now you flash forward and as painful as the passage of time can be, we now have truly advanced DNA testing available. We have forensic genealogy available."

Still, he can’t help but wonder what might have been.

"I look around now and there are all of these amazing women in the United States and around the world doing incredible things," said Thomas. "And it saddens me that Cathy Thomas would have been one of those women. She had everything going for her. She was brilliant, beautiful and well-educated, but she was also thoughtful, modest and a deep thinker. And it pains me to think that 34 years have gone by now. Cathy has been gone longer than she was with us. And in these 34 years, she would have done amazing things."

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The two-night special premiere of "Lovers’ Lane Murders" airs Feb. 11 at 9 p.m. and 10 p.m. ET on Oxygen. The second night airs Friday at 9 p.m. and 10 p.m. ET.