Gavin de Becker, seen here on "Oprah" in 2008, is heading Jeff Bezos's investigation into the National Enquirer's acquisition of his private texts.

This story has been updated.

Park Dietz recalled meeting Gavin de Becker in 1983, when Dietz was a young forensic psychiatrist researching the delusions of stalkers, and de Becker was an up-and-coming security consultant to Hollywood stars.

De Becker had fewer than two dozen celebrity clients at the time, Dietz recalled, but thousands upon thousands of deranged letters, stuffed into storage bins at his home in the Los Angeles area. Dietz and his assistants spent the summer in a movie trailer set up in the driveway, sifting through recorded insanity. “It was extraordinary,” Dietz told The Post.

Among the ramblings and threats of violence were live rifle cartridges, fake bombs and a tape of the sender “speaking to the celebrity in a halting manner with music in the background,” as Dietz recorded in his final report.

Thirty-two letter writers had sent poems. Four had sent utility bills. One had enclosed a dog’s head.

“Nobody had ever studied such a thing before,” Dietz said. “And de Becker had gotten interested in this all on his own.”

In decades to come, de Becker’s collection of letters would grow to occupy a warehouse — and his client list would swell until he became arguably the world’s foremost expert on threatening messages.

Now he is also at the center of investigations into a different kind of threat — the National Enquirer’s alleged extortion attempt against Amazon founder Jeffrey P. Bezos.

Bezos, who owns The Washington Post, hired de Becker this year to find out how the Enquirer obtained private texts showing his relationship with former TV anchor Lauren Sanchez. On Thursday, the billionaire published emails that appear to show the tabloid threatening to publish intimate photos unless he ends de Becker’s probe.

The source of the tabloid’s fury, according to the emails, were reports about de Becker’s view that the Enquirer’s story was politically motivated and linked to associates of President Trump.

De Becker has spent decades investigating those trying to intimidate his clients in Hollywood, the business world, and even Planned Parenthood in one early case. Described by Bezos as “one of the smartest and most capable leaders I know,” the security guru emerged from a violent childhood to essentially create a new industry of threat prediction.

In his best-selling 1997 book “The Gift of Fear,” de Becker describes being physically abused for years by his mentally ill, drug-addicted mother. As a child, he wrote, he once watched as his 33-year-old mother repeatedly shot his stepfather.

“His hands were held out stiffly in front of him as if they could stop bullets. I remember wondering for a moment if it would hurt to be shot,” he wrote.

The stepfather survived, but de Becker’s mother continued to beat him viciously, he told the Los Angeles Times in 2002, before she killed herself when he was 16.

This personal trauma merged with 1963 assassination of President John F. Kennedy, which de Becker later told the Los Angeles Times “was the first world event that had any impact on me personally,” and left him fascinated with trying to keep public figures safe.

De Becker’s grandfather rented a Beverly Hills apartment so he could attend the local school district, where he made friends with future stars such as Carrie Fisher and made his first moves into celebrity protection. Rosemary Clooney invited him to move in after his mother’s death and he became her “de facto road manager,” the Times reported. Clooney’s son, the actor Miguel Ferrer, later used de Becker as a model for his “Twin Peaks” character, FBI Agent Albert Rosenfield.

Soon he was working security for the likes of Elizabeth Taylor, Shaun Cassidy, and Dean Martin’s ex-wife, Jeanne Martin.

“Gavin turned that whole business around and invented it, really. He ran a protective detail the way the Secret Service would operate,” Cassidy told the Times.

He founded his now-famed firm, Gavin de Becker and Associates, in 1978. John T. Monahan, a University of Virginia psychologist who also specializes in threat assessment, recalled meeting him around that time, and being impressed enough that the two men remained in contact for decades. “He is a true pioneer in the area of threat assessment,” Monahan said. “It does not surprise me at all that Jeff Bezos would call upon his expertise.”

Faye Wattleton recalled meeting de Becker in the 1980s, when she was president of Planned Parenthood, then facing a nationwide spree of threats — plus several bombings and burnings — against its clinics.

“There was a lot of anxiety,” Wattleton recalled. She said de Becker designed new security procedures at Planned Parenthood’s New York headquarters and advised branches across the country — psychologically preparing clinic workers for an era of violence.

“People really liked the way he dealt with their anxieties,” Wattleton said. “He didn’t come as if he was on the beaches of Normandy. He was very professional.” And when de Becker’s contract ended, she said, she had the distinct impression she’d hear his name again. “He was definitely an up-and-comer.”

And she was right. Within a few years of establishing his company, de Becker’s research was acclaimed enough that President-elect Ronald Reagan hired him to protect guests at his first inauguration, the Times reported, and then invited him onto a Justice Department advisory board. By the end of the decade, he would count the likes of Robert Redford, Jane Fonda and Joan Rivers as clients.

He worked carefully to sort the threats those celebs faced into categories, from harmless superfans to legitimately dangerous characters. And the method he worked out soon blossomed into a unique tool: the MOSAIC threat assessment systems. He saw the program as a direct extension of the skills he had learned watching his mother — a systematic way to anticipate bloodshed.

“The way I broke down the individual elements of violence as a child became the way the most sophisticated artificial intuition systems predict violence today,” he wrote in “The Gift of Fear.” “My ghosts had become my teachers.”

In its early days, his programs were largely used by police to protect high-risk residents like politicians or judges, the Los Angeles Times reported in 1997. De Becker later expanded MOSAIC to profile domestic abusers and to try to curb violence in schools. Now, MOSAIC is available as a free online questionnaire that can be used by anyone interested in obtaining “comprehensive assessments” of threats.

As de Becker worked to protect celebrities, he sometimes came into direct conflict with the tabloid papers that aggressively cover them — including the National Enquirer. In 1990, the tabloid faced lawsuits from Taylor and Roseanne Barr, and a wave of stories alleging the paper paid people to be phony sources.

The paper’s editor at the time, Iain Calder, had a scapegoat for all the drama: de Becker. “There are a powerful group of celebrities that have put together a war chest and gone to Gavin de Becker to go after us,” Calder told the Associated Press in 1990.

“The idea of 100 major media figures gathering in a gymnasium . . . shouting ‘Give me the head of the National Enquirer’ is absolutely ridiculous,” de Becker scoffed in an interview with the AP.

But he earned a reputation of being willing to go to incredible lengths for his clients — for both security and privacy. When George Harrison was gravely ill in 2001, de Becker arranged for him to retire to a secret location — the address so closely guarded that even close friends had to go to a fictitious address first and then be escorted there, the Los Angeles Times reported. The consultant took public heat when that nonexistent address made it onto Harrison’s death certificate that same year.

The consultant’s own celebrity rose precipitously in 1997, when “The Gift of Fear” rocketed up bestseller lists after Oprah Winfrey endorsed it and invited him onto her show. The book delves into the lessons de Becker has learned from studying violence, while bemoaning a United States that seems addicted to it.

“It is an unusual firm,” he writes of his operation, “one that could only exist in America and, in most regards, need only exist in America.”

Few of de Becker’s famed investigations have approached the ongoing Bezos case in terms of sheer public interest, though. As Bezos wrote Thursday on Medium, he asked the consultant to figure out how the Enquirer had obtained his private texts after the tabloid published its report on his relationship with Sanchez.

“I’ve known Mr. de Becker for twenty years,” Bezos wrote. “I asked him to prioritize protecting my time since I have other things I prefer to work on and to proceed with whatever budget he needed to pursue the facts in this matter.”

That investigation, as The Post reported on Tuesday, led de Becker to point the finger at Michael Sanchez, Lauren’s brother. Michael Sanchez is a “pro-Trump Hollywood talent manager,” The Post reported, who is acquaintances with Roger Stone, Trump’s longtime ally who was recently indicted by special counsel Robert S. Mueller III, and former Trump adviser Carter Page. De Becker told the Daily Beast that “strong leads point to political motives” behind the Enquirer story.

In the emails published by Bezos, officials for American Media Inc., the parent company of the National Enquirer, demanded that both he and de Becker renounce those claims. Instead, Bezos made the demands public.

De Becker declined to comment for his article. As the turmoil rages over Bezos’s claims, the foreword to the Kindle edition of de Becker’s 1997 bestseller may offer another window into his view of the proceedings.

“Most human predators . . . seek power,” he writes. “To destroy or damage something is to take its power. This applies equally to a political movement, a government, a campaign, a career, a marriage, a performance, a fortune, or a religion. "

“To push a pie into the face of the world’s richest man is to take his power,” he adds, “if only for a moment.”

Dietz, the psychiatrist who met de Becker in 1983, went on to become something of a celebrity expert himself, working on the Unabomber case and the Beltway sniper shootings, among many others.

Among the deranged letters, bodily fluid and animal parts he catalogued in de Becker’s driveway trailer, Dietz said, “even then in his files were tabloid clippings — and a recognition that the tabloid’s interest in celebrities caused them to behave in ways similar to the adversaries who were stalking celebrities.”

Allyson Chiu contributed to this report.