James Holland, the Texas Ranger who helped crack “the most prolific serial killer in U.S. history,” is breaking his silence on how he finally got the murderer to confess.

Samuel Little was interviewed repeatedly by Holland, dubbed the “serial killer whisperer,” from June 2018 until shortly before Little’s death in December 2020, according to the Texas Department of Public Safety. During those sessions, Little confessed to killing 93 people between 1970 and 2005. 

More than 60 of those confessions have since been matched to victims through DNA evidence and corroborating interviews, authorities said.

JOURNALIST’S DANGEROUS OBSESSION WITH A FORGOTTEN SERIAL KILLER UNRAVELED HER REALITY

Now retired, Holland is hosting a new true-crime series on Investigation Discovery (ID), “Killer Confessions,” which examines the interrogation tactics and pivotal moments that defined his career.

Holland was initially asked to question Little about a killing he didn’t commit. During more than 700 hours of interviews, Little revealed details of dozens of other slayings only the real perpetrator could have known.

“Samuel Little was the epitome of evil,” Holland told Fox News Digital. “He was a mean, horrible person. He was the ultimate predator — a killing machine. He was really smart and had a very distinct photographic memory.”

WATCH: FBI SAYS SAMUEL LITTLE IS WORST SERIAL KILLER IN US HISTORY AFTER HE CONFESSED TO 93 MURDERS

“Some people would have falsely looked at him and said he was just primarily picking up prostitutes,” Holland shared. “But that’s not necessarily true. A vast number of these victims were not prostitutes. They were people he met every day.

“His ability to win people over with his persona, one that manipulated and controlled them? I don’t know how to describe him other than as an ultimate apex predator because he wasn’t bothered by anything.”

Little was in failing health while serving a life sentence in a California prison when Holland was asked to interview him. The former boxer, who used a wheelchair to get around, had refused to speak with other authorities and initially reacted the same way to Holland.

“The first time I stepped into that room, he was not happy to see me,” Holland recalled. “He’d get information from you, then send you packing, overwhelming you with anger and threatening tones. He was automatically that way with law enforcement.”

Despite Little’s attempts to assert dominance, Holland never flinched. Little tested the veteran investigator by describing in graphic detail how he killed a woman while locking eyes with him. Holland remained stone-faced, listening.

“The first part of dealing with him was getting through the shock in that room with him,” Holland explained. “You couldn’t react to his negativity. When you deal with a serial killer, there’s no remorse. If you start talking to them about remorse, they think you’re speaking Martian. They don’t understand that, can’t comprehend it. They’ll immediately shut down.

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“Little treated it all like a game,” Holland continued. “Was he going to try to scare the hell out of me or recant the murder he’d just confessed to? He wanted to shock me. He’d throw things and study my face to see how I’d react, deciding whether I was ‘worthy’ of hearing more and whether I thought horribly of him. It was the ultimate acting job for me because I had to keep a completely blank face. He would just stare at me.

“He used the word ‘monster’ all the time. He didn’t want me to think he was a monster, which obviously he was. But I just couldn’t let him know what I was thinking.”

Food played a role in Holland’s strategy, according to The Associated Press. During hundreds of hours of interviews, he brought pizza, Dr Pepper and grits — Little’s favorite snacks — and talked sports as Little ate. He also assured Little he wouldn’t be executed and addressed him by his childhood nickname, “Sammy.”

Little, who called Holland “Jimmy,” began to open up.

“When I found something that entertained him, he was intrigued,” Holland said. “That would open the door. The strange thing is, if you blocked out who he was, you could almost enjoy talking to him. He was insightful and funny, and he told great stories. It was easy to forget, at times, how evil he really was. But he was a monster who had no remorse for his killings. You always had to keep that in the back of your mind.

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“He was always trying to get into your head,” Holland recalled. “For me, it was the ultimate game of Sudoku because I was always thinking ahead and putting myself one step ahead of him.

“These serial killers like Little are convincing and manipulative. That’s why they get away with it. And they’re smart. With Little, he was already thinking about DNA before the technology existed. He was careful in what he did and where he left his victims.”

During their conversations, Holland said he was careful never to bring up remorse or discuss the victims as actual victims, and the tactic worked.

“If you break that rule, step over that boundary, you can never go back into the room with them,” he said. 

“I think, so often, detectives step into the room and lean in on remorse, their moral psyche. That’s generally how confessions occur. You talk about the victim, you talk about the lack of sleep from remorse. But if you take that into a room with a serial killer, you’re done. You can’t come back from that.”

Little was a career criminal who had spent decades in and out of jail. When he wasn’t behind bars for larceny, assault, drug offenses or other crimes, he traveled the country, according to the AP.

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Little said he committed his first killing on New Year’s Eve 1970 in Miami and his last in 2005 in Mississippi. According to the AP, he also killed victims in Tennessee, Texas, Ohio, Kentucky, Nevada and Arkansas, among other states.

In 2012, Little was arrested on drug charges, and his DNA linked him to three killings in California.

As Little opened up to Holland, he provided dozens of paintings and drawings of his victims, sometimes scribbling their names and details such as the year they were killed and where he left their bodies.

“He always remembered where he met the person, the moment he killed them and what their last words were,” said Holland. “He always remembered where he dumped the bodies. And this is 40-plus years later, someone who’s using drugs and alcohol at different points in time. The majority of these crimes were matched up by his descriptions of the crime scene.

“The way he described where he left the bodies and then looked at these crime scene photos,” Holland paused. “It’s mind-numbing. He relived these crimes through his memories. We were able to match so many of those cases because he described the crime scene. And when you looked at the case files and read the reports, there were descriptions of Samuel Little in a witness account.”

As Little kept talking, authorities across the country rushed to reopen cold cases, relying on DNA evidence to prove his guilt. With his health failing, the clock was ticking. Investigators tracked down relatives and brought long-awaited closure to many families. Little later told the Los Angeles Times he had “found a friend in a Texas Ranger.”

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Little died in 2020 at a California hospital. He was 80. He was serving a life sentence for multiple counts of murder.

“He had no remorse,” said Holland. “I had to convince him I was OK with that, which is still a very difficult thing to talk about. But I had to convince him he wasn’t destroying my mind. I just needed him to talk. And that’s what he did.”

“Killer Confessions: Case Files of a Texas Ranger” airs Tuesdays at 10 p.m. and streams the next day on HBO Max.