Joseph Naso, the “Alphabet Killer,” may have been paying twisted homage to a death row inmate.

The assertion was made by retired FBI task force investigator Ken Mains, who is attempting to solve cold cases that may be linked to the 91-year-old. Naso’s crimes are explored in the new Oxygen true crime docuseries, “Death Row Confidential: Secrets of a Serial Killer.”

Naso is a former photographer convicted in 2013 of killing four women.

The view up Medgar Avenue in Black Springs, Nevada, shows the former home of Joseph Naso, the first house on the left, in 2011. Naso is on death row in California. (Karl Mondon/Media News Group/East Bay Times via Getty Images)

For Mains, it’s crucial to solve the cases before Naso takes any secrets to the grave. In the documentary, Mains is seen sitting down with family members, who have spent decades searching for answers about their murdered loved ones.

“It was emotionally difficult,” Mains admitted. “You get the brunt of their anger, their love, their hate. … But just because something’s difficult, it doesn’t mean you run from it. So I was happy to sit there and tell them what happened.”

Mains hopes the documentary raises awareness about the cold cases and his quest to solve them.

Joseph Naso has since been moved from San Quentin State Prison in Marin County, Calif. (Smith Collection/Gado/Getty Images)

“It’s not about me solving these cases,” said Mains. “That’s what I do. That’s what I’ve done for decades. The bigger story is Bill Noguera and what he was able to do from behind prison walls. He was punished for killing someone when he was 18, and now he wants to give back. He’s in his 60s and wants to help. That’s what he did, and that’s what he continues to do.”

“The bigger story is what you can do with your life,” Mains said. “… Redemption is possible. And for the families, their loved ones are not forgotten.”

“Death Row Confidential: Secrets of a Serial Killer” is available for streaming on Peacock. Fox News Digital’s Stepheny Price contributed to this report.