One of William Keck’s biggest regrets was reporting on Dack Rambo’s final tragic months.

The TV heartthrob, who starred on “Dallas” and “Another World,” died in 1994 after disclosing that he had tested positive for AIDS. He was 52. 

“There are so many stories that I was not proud to have my byline associated with,” the former reporter for the National Enquirer told Fox News Digital. “The main one is what I called ‘Chapter 11’ in my book, which is very appropriate that I called it Chapter 11 because it was my moral bankruptcy.”

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Keck has written a new memoir about his decades-long career, “When You Step Upon a Star: Cringeworthy Confessions of a Tabloid Bad Boy.” In it, he details the celebrities he befriended, protected and wronged.

“I was mortified,” Keck admitted about reporting on Rambo’s final months. “That was a shameful indoctrination into the Enquirer.”

According to the book, Keck received an anonymous phone call from a woman alleging that she worked at a medical center in California where she had access to patient records. One of the records belonged to “a TV star from a long-running, successful primetime soap opera who was in the final stages of AIDS.”

William Keck’s book, “‘When You Step Upon a Star: Cringeworthy Confessions of a Tabloid Bad Boy,” is out now. (Jacobs/Brown Media Group)

Keck described how, several years ago, the National Enquirer scored several cover stories on Rock Hudson before he died from the same disease.

“With that in mind, I knew this could potentially be another big tabloid story,” Keck wrote. “And I was also fairly certain I knew the secret identity of the dying actor.”

The book noted that in 1991, Rambo, who played J.R. Ewing’s cousin Jack Ewing in “Dallas,” came out publicly as bisexual and HIV positive. Keck was certain that the mystery actor was Rambo, and he was “spot-on.”

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Dack Rambo (left) is seen here opposite Larry Hagman (right) in “Dallas.” (ALAMY)

It didn’t take long for Keck’s story to get the green light.

“According to my source (whose mother, it turned out, was the one who actually worked at the hospital as a nurse), Rambo had been checked in by a male friend the night before,” Keck wrote. “Because of his weakened condition, he could only scratch an X on the forms in place of his signature. He’d tried to shield his carcinoma-covered face behind a sheet, and though alert, appeared confused.

“For the initial tip, the caller was to receive a guaranteed payment of $860, with a $400 bonus should the story appear on our cover, which was pretty much a guarantee if we succeeded in our nefarious mission: to land Dack Rambo’s exclusive deathbed interview!”

Dack Rambo with Priscilla Presley in “Dallas.” (ALAMY)

“This assignment was about as horrible as they came, made all the worse because it was centered around a man I greatly admired,” Keck continued. “And not only that, the subject matter was treading dangerously close to my own secret life that I’d been desperately trying to shield from my mother, friends, co-workers and the rest of the world.”

In the book, Keck wrote that the source had supplied him with Rambo’s room number at the hospital. But once he arrived, the bed was empty.

Keck claimed that while he didn’t come face-to-face with Rambo, the outlet still published a “last interview” with the ailing star that had his byline attached to it. In the book, Keck claimed the story had been “poorly written” and “completely fabricated.” A spokesperson for the outlet didn’t immediately respond to Fox News Digital’s request for comment.

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Dack Rambo attends the Seventh Annual Nancy Reynolds Awards on November 13, 1991, at the Beverly Wilshire Hotel in Beverly Hills, California. The actor died in 1994 at age 52. (Ron Galella, Ltd./Ron Galella Collection via Getty Images)

“The article came out a few weeks before Dack’s valiant battle ended in March 1994 at age 52 in his hometown of Delano, CA,” Keck wrote. “Whatever last words, if any, were actually spoken by the once gorgeous silver fox with a perfectly placed mole on his left cheek, we’ll never know. In the years since, the actor’s mother, Bea (who’d already buried Dack’s twin brother, Dirk, following a tragic 1967 auto accident) and his siblings, Bill and Beatrice, all passed.”

“Even though the article painted Rambo as a proud, brave, grateful and benevolent soul who died with dignity, they weren’t his words and never should have appeared in print,” Keck claimed in the book.

Keck told Fox News Digital that he never heard from Rambo’s family after the story went to print.

LOS ANGELES – JUNE 7: Twin brothers (from left) Dirk Rambo and Dack Rambo for “The Loretta Young Show” in 1962. Dirk died in 1967 at age 25. (CBS via Getty Images)

“I think I certainly would’ve heard from the family if they were furious about the story … that was completely fabricated,” he said. “This was a rural family. They had already gone through the loss of Dack’s twin brother in a motorcycle accident at an early age. So this was a family grieving. I think they probably just decided to bury their heads. Maybe they weren’t even aware. I don’t know. Maybe they weren’t even alerted that this article had happened.”

“I’m very sad,” Keck admitted. “I researched to see if any of his relatives were still living. Dack’s mother passed away a while ago. His two surviving siblings have since died. I would’ve really loved to apologize to them for … what I was a witness to.”

In the book, Keck claimed he “didn’t write a single word of the story” despite the fact that it was attributed to him “for everyone to see.” Keck also claimed that he tried to intervene before the story went to press but was unsuccessful.

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Dack Rambo starred opposite Morgan Fairchild in “Paper Dolls.” (S Karin Epstein /American Broadcasting Companies via Getty Images)

“I’m well aware that confessing the role I played in this unforgivable transgression will win me no fans, and perhaps even understandably lead some to question the authenticity of the other stories in this book,” he wrote. “That’s your choice. I’ve already told you everything within these pages is true.”

Keck’s book features a statement from “Dallas” actress Sheree J. Wilson to help “set the record straight” about Rambo’s life and legacy. Wilson played Rambo’s ex-wife in the series.

“Dack was so charming and had this smile that was infectious,” Wilson recalled, as quoted in the book. “Just as sweet as the day is long. My very first scene was with Dack, and — as you can imagine — I was terribly nervous about joining this long-running show I’d watched since high school. Even though we were playing adversaries, he couldn’t have made me feel more comfortable. He told me, ‘Just relax. We’re all friends here and you’ll find that to be true.’”

Sheree J. Wilson with William Keck. (Courtesy of William Keck)

Wilson described how she had been stunned to learn of Rambo’s death.

“Dack was so fit, good-looking and seemed the epitome of health,” wrote Wilson. “It was way too soon and just heartbreaking. But for Dack to make the brave choice to be among the first to use his celebrity to educate people and to bring awareness to AIDS — so that there wasn’t as much stigma and fear and judgment — took tremendous courage. Especially in the darkest days when it was happening to him.”

“That is his legacy,” Wilson added.

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According to reports, Dack Rambo was diagnosed with AIDS in 1991. (Bob DAmico /American Broadcasting Companies via Getty Images)

In 1991, Rambo quit his role as Congressman Grant Harrison on NBC’s “Another World” after revealing his AIDS diagnosis, Variety reported. According to the outlet, Rambo said that going public with his condition was “like freedom to me.”

Keck told Fox News Digital he was eager to finally tell the truth.

“I told the stories back in the day, and this is what happened behind the scenes,” said Keck. “The only secrets I’m revealing are my own, the things that I regret, the things that I did to get the story. And I’m apologizing. In certain cases, I was able to reach out to these people and apologize. So it’s really about the power of change. . . . I have a lot of celebrities who commend me for having the bravery to do this.

Dack Rambo appeared on “Dallas” from 1985 to 1987. (Getty Images)

“I think this really makes it different from other books. There are a lot of celebrity tell-alls, but a reporter telling their own secrets and taking responsibility for those mistakes and showing you can change? I hope that’s inspiring to people.”