Friday, Nov. 12, 2021, started as a fun night in Los Angeles for architect Hilda Marcela Cabrales, 26, and her friend, 24-year-old model Christy Giles. The pair headed out to a nightclub in Hollywood and then to a warehouse party in East Los Angeles to see a DJ they both loved.

Christy's husband, Jan Cilliers, was in San Francisco that weekend visiting his father. He says Christy and Hilda, who was new to Los Angeles, were becoming "fast friends."

But what started as a happy girls' night out took a sinister turn, Cilliers says, when he woke up that Saturday morning in San Francisco to see his wife's phone location at a Los Angeles address he didn't recognize. He and Christy always shared locations, he says, for safety reasons.

Cilliers says he texted Christy and didn't hear back. And, as the hours mounted without a word, Cilliers says, his fear began to grow.

What happened that weekend and the tragic aftermath is investigated by "48 Hours" and contributor Jonathan Vigliotti in "Dead Girls Don't Talk." An encore of the broadcast airs Saturday, June 20 at 10/9c on CBS and streaming on Paramount+ (folllowing the WNBA on CBS.)

Cilliers says he experienced "raw panic" when, at around 5 p.m. on Saturday, Nov. 13, he says he saw Christy's phone had moved to a hospital about three miles from that strange address. Cilliers soon learned that Christy had been dropped there by two masked men in a black Prius without license plates. They said they found her unconscious on the street nearby and were being "good Samaritans." Doctors had declared Christy dead on arrival.

"So, in less than 24 hours, your world was turned upside down?" asks Vigliotti.

"Shattered, yes," Cilliers replies.

Hilda also had a habit of sharing her phone location — with a close friend who was also her emergency contact. That friend also became concerned on Saturday, when she saw Hilda's phone pinging at 8641 West Olympic Boulevard — the same address where Cilliers had tracked Christy's phone.

Hilda's friend soon learned that Hilda, like Christy, had been dropped off at a hospital by two masked men driving a black Prius with no plates, who said they had found Hilda passed out on the street.

Hilda was still alive, but in critical condition. Two weeks later, with no sign of regaining consciousness, her family made the difficult decision to take Hilda off life support. Her sister, Fernanda Cabrales-Arzola, said she remembers telling Hilda it was OK to leave and that she told Hilda, "Thank you for being my sister."

Hilda's family decided to donate her organs, and her mother, Dr. Hilda Marcela Arzola-Plascencia, said she remembers the medical team lining the hallway and "clapping. To honor her for giving life."

Because both Cilliers and Hilda's friend knew exactly where the two women had been all day, and because they knew the minute each woman was taken to each hospital, when LAPD detectives got the call about the two cases, they had a huge head start.

Within hours of Hilda being dropped off at that second hospital, LAPD homicide detective Jonathan Vander Lee and his partner were on their way to 8641 West Olympic Boulevard. By the time they arrived, they knew it was the home of David Pearce and that he owned a black Prius. Pearce lived there with a roommate named Brandt Osborn.

A month later, Pearce and Osborn were arrested in connection with the two women's deaths. Pearce was eventually charged with two counts of felony murder and Osborn, who was seen helping Pearce take both women out of their home and dropping them off at both hospitals, was charged with accessory to murder after the fact.

It took a little more than three years for their cases to go to trial, but in the end, Pearce was convicted of murdering Christy and Hilda and of raping seven other women who came forward to testify at the trial. The jury deadlocked on a verdict for Osborn, and a mistrial was declared for his case.

At a press conference after Pearce's conviction, Christy's mother, Dusty Giles, pleaded with the public to learn the safety lesson from her daughter's case, saying, "As much as it hurts to lose my baby girl ... her sharing her location technology told us where she was."

Police say that information was critical to helping get Pearce, whom prosecutors say was a serial rapist, finally off the street.

Dusty Giles begged the public to learn the lesson from their horrendous loss, "Please, within your own families ... share locations," she said, adding, "You'll never know when you're going to not be able to get in touch with somebody."

Pearce has not yet been sentenced, and the district attorney has not announced if Osborn will be retried.