Barbara Nantais, 15, was a popular sophomore at her high school in Lakewood, Calif., and had just made the varsity cheerleading squad.

Barbara Nantais had four siblings; older sisters Lorraine and Sue and younger brother Tom.

Barbara Nantais, far right, with her sisters Sue, Lorraine and mother Judy.

Barbara Nantais and Jim Alt had been introduced by Barbara's sister, Sue. Sue describes Barbara as smart, outspoken and strong-willed.

Jim Alt, 17, was very popular at his high school in Long Beach, California. Friends describe him as "the life of the party."

Barbara Nantais and Jim Alt were accompanied to the beach by 19-year-old Rick Selga, pictured, and his girlfriend.

A lifeguard tower on beautiful Torrey Pines State Beach in San Diego.

Around 9:30 p.m., Barbara Nantais and Jim Alt went down to the beach for some privacy and Rick Selga and his girlfriend stayed in the parking lot to sleep in the station wagon. The next morning Rick was awoken by Alt knocking on the car window.

Jim Alt had been severely beaten with rocks and/or logs from the fire pit on the beach. Rick Selga says he only recognized his friend through his blonde hair because his face was so badly injured.

Rick Selga ran to the beach looking for Barbara Nantais, and found her murdered. Barbara had been beaten, sexually assaulted, strangled and one of her breasts had been mutilated.

Barbara's parents, Ralph and Judy Nantais, were devastated by the news. They were out of town and had left their children in the care of an adult family friend. They had no idea that Barbara and Jim had gone to the beach to camp.

Jim Alt was rushed to the hospital where he had emergency surgery. He spent days in a coma and when he awoke, he had no memory of the attack. He was briefly investigated, but ruled out as a suspect because his injuries had been so severe and life threatening.

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Despite the brutal attack, there was little evidence and the case eventually went cold. Six years later, on Aug. 24 1984, Claire Hough, a 14-year-old from Rhode Island, was found murdered on the same beach.

Although Claire Hough was from Rhode Island, she had spent a lot of time on Torrey Pines Beach. This is a picture of Claire as a toddler with her mother, Penny, at that beach.

Claire Hough's attack had been similar in many ways to the attack on Barbara Nantais. Both girls had been sexually assaulted, beaten, strangled and had their breasts mutilated.

Claire Hough's best friend, Kim Jamer, had spent a few days with Claire in California but had returned to Rhode Island before the murder. Jamer says she had a very bad feeling on the beach at night two days before Claire was killed and had warned her friend not to go there after dark.

Kim Jamer says Claire Hough loved 1980s rock music and had a closet full of posters and magazine clippings of Kiss, Van Halen, Journey, and Ozzy Osbourne.

Claire's parents, Penny and Sam Hough, say their daughter had an innate sense of justice and she was known as the class mediator. Friends who got into arguments would often ask her to adjudicate.

Claire Hough, pictured in the blue wig at a parade when she was younger, had an "inner light" according to friend Kim Jamer.

Despite the similarities in the Claire Hough and Barbara Nantais murders, their families did not know about each other. But around 2008, the San Diego Police Cold Case Unit posted the cases on its website saying that they believed both girls had likely been murdered by the same killer.

The two cases were cold until 2012, when advanced DNA testing identified two DNA hits on Claire Hough. Blood on Claire's jeans was linked to a convicted rapist named Ronald Tatro.

The other DNA hit, a microscopic amount found on a vaginal swab, was linked to a man named Kevin Brown. Brown had been a criminalist in the San Diego Police Department lab before retiring in 2002.

According to the police affidavits and search warrants, Kevin Brown had also made several incriminating statements during the investigation.

Kevin Brown had been married for over 20 years to Rebecca Brown when police came knocking.

Rebecca Brown strongly believes in her husband's innocence and argues he was not a killer or a rapist. Rebecca describes Kevin as gentle, soft spoken, nervous, shy, and one of the "good guys."

Lawyers for Rebecca Brown and Kevin Brown contend the San Diego Police Department's case is built on rumors and misinterpretations. Gene Iredale and Gretchen Von Helms say cross-contamination in the lab was to blame for the DNA link.

Today, the Houghs would rather not focus on the details of their daughter's murder. What is important to Sam and Penny Hough is who Claire was. They say Claire was all about love which is evident in the will she left behind telling her family and friends how much she cared about them.

For her parents and the people who knew her, Claire Hough will always be remembered as smart, vibrant, spirited, loving, and a defender of the wronged. She "had a lot of potential."

The Nantais family remembers Barbara as beautiful, popular, smart, stubborn and someone who had a "mind of her own."

Her case remains open. Anyone with information is urged to contact San Diego County Crime Stoppers at 888-580-8477.

WATCH: Family shares memories of Barbara Nantais

WATCH: Blood in the Sand

Jim Alt, who survived the brutal attack the night Barbara Nantais was murdered, struggles with what happened and is dedicated to helping other survivors through his Facebook page, "Surviving Victims of Violent Crimes."