The plea deal reached by Idaho state prosecutors with admitted murderer Bryan Kohberger may have appeared as justice to some, yet the agreement left bereaved families and numerous Americans feeling shortchanged.

Although Kohberger, 30, is set to receive a life sentence on July 23, the nation will never be revealed the complete extent of the evidence against him and, primarily, an explanation for his actions: why?

What was it that drove Kohberger, a former teen heroin addict turned health freak criminology student into a quadruple murderer?

In an exclusive conversation with the Daily Mail, renowned author James Patterson discloses the theory he and investigative journalist Vicky Ward formulated in their latest book, ‘The Idaho Four: An American Tragedy.’

The work is a forensic account of what happened in the early morning hours of November 13, 2022, when Kohberger slipped into 1122 King Road in Moscow, Idaho and stabbed 21-year-old Maddie Mogen, Kaylee Goncalves, 21, Xana Kernodle, 20, and her boyfriend Ethan Chapin, 20, to death.

And now for the first-time, Patterson and Ward report that while Kohberger hadn’t killed before – he had, perhaps, long been preparing for this unspeakable crime.

While Kohberger, 30, will be sentenced on July 23 to life in prison, the country will never be presented with the full scope of the evidence against him and, above all else, an answer to the question: why?

Kaylee Goncalves, Madison Mogen, Ethan Chapin and Xana Kernodle were stabbed to death in their beds as they slept

Now, in an exclusive interview with Daily Mail, best-selling author James Patterson reveals the theory that he and investigative journalist Vicky Ward developed in their new book, ‘The Idaho Four: An American Tragedy.’

For the book claims that Kohberger had burglarized the homes of the parents of two of his friends in Pennsylvania, including the house of former Navy SEAL Mark Baylis.

‘Even though he’s a Special Forces veteran with skills and experience, he cannot catch the person who is repeatedly stealing his knives, his coins, his prescription pills, his girlfriend’s jewelry. It maddens him,’ Patterson and Ward write.

‘Baylis talks to his son Jack and his nephew Brandon about the thefts,’ the book reports. ‘He says he’s going to catch the thief if they try again. Shoot him. Jack tells the third kid, whose name is Bryan, that his dad is p***ed.’

It is at this time that Baylis believes that someone has begun to stalk him.

‘The stalker hides in those trees, camouflaged, munching on Reese’s Peanut Butter Cups, dropping the wrappers on the ground, waiting for Mark to leave on one of his orange motorbikes or in his pickup truck,’ they write.

‘The stalker forces the door open with a knife and heads for the bathroom, where Baylis keeps old prescription drugs.’

Baylis even reportedly thinks that he nearly once caught Kohberger – an addict known to steal to feed his habit – in the act. But Baylis suspects Kohberger escaped without being seen.

‘He comes to believe that Bryan, knowing he has the element of surprise on his side, hides, waits for the veteran to walk toward the back of the house, then sprints out the front door and into the woods he knows will protect him,’ the book says.

Surveillance, breaking and entering and narrow escapes. These are all the skills that Kohberger employed decades later to horrifying effect.

‘I think he cased the [King Road house]. He figured it out,’ said Patterson.

‘He’d done several break-ins in Pennsylvania and what did he do in Idaho? The door was open. He just had to slide it.’

For the book claims that Kohberger had burglarized the homes of the parents of two of his friends in Pennsylvania, including the house of former Navy SEAL Mark Baylis. (Pictured: Kohberger in Pennsylvania as a teen)

Surveillance, breaking and entering and narrow escapes. These are all the skills that Kohberger employed decades later to horrifying effect. ‘I think he cased the [King Road house] (pictured above). He figured it out,’ said Patterson.

But who was the target?

After 300 hours of interviews and months of intense research, Patterson and Ward believe they have an answer to that question too.

‘There was a vegan restaurant in town [The Mad Greek] where Maddie and Xana both worked. And we suspect he may have been there,’ Patterson explained.

Maddie’s friends shared their personal beliefs with the authors that Kohberger may have asked Maddie out and that she rejected him. The thought torments them, they told Patterson, like ‘a recurring nightmare.’

Her family had previously noted that Kohberger followed Maddie – a prolific Instagram poster – on social media and ‘liked’ many of her pictures.

‘I believe he watched Maddie and he cased the house,’ Patterson said.

Cell phone records put Kohberger in the vicinity of the students’ house between 10pm and 2am at least a dozen times between August and November that year.

Under cover of darkness, Patterson said, Kohberger may have watched his prey unseen.

Trees behind the student house offered a perfect screen and Maddie’s open blinds provided a clear view into her room – flagged as hers by the letter M and her pink cowboy boots which were perched in the window.

‘She would be very visible from the road, doing her hair, doing her makeup,’ he explained. It was the perfect set-up, Patterson said, for ‘Bryan the Peeping Tom.’

Maddie’s (pictured, right) friends shared their personal beliefs with the authors that Kohberger may have asked Maddie out and that she rejected him. The thought torments them, they told Patterson, like ‘a recurring nightmare.’ (Pictured: Madison Mogen, right. Kaylee Goncalves, left)

While Patterson and Ward paint the students as popular, driven and loved, they depict Kohberger as an angry, increasingly disturbed, incel [involuntary celibate] whose life was spiraling in the weeks leading up to the killings.

Indeed, the 30-year-old criminology post-grad, who worked as a teaching assistant at Washington State University in nearby Pullman, had a history of displaying concerning behavior towards female students.

He graded them poorly, wrote condescending ‘essays on their essays,’ and had expressed the view that women had no business being in the class.

The behavior led to a formal complaint being made about him to the faculty and disciplinary proceedings that, in the days before the murders, saw Kohberger on the cusp of losing his coveted position.

‘He’d been angry for a long time. I think he’s one of those people that goes back and forth between thinking that he’s worthless and thinking that he’s God. He’s certainly a narcissist,’ said Patterson.

‘I think it was a combination of all these things and his life was about to get thrown up in the air. He was about to lose his fellowship and probably get thrown out of school. He was angry and he thought he could get away with it.’

Truth be told, Patterson said; he almost did.

In his opinion, Kohberger very nearly committed ‘the perfect crime.’

Nearly.

‘I don’t think Kohberger went in there expecting to kill four people,’ said Patterson. ‘Maddie was the target, and he went right to her.’

But Kaylee had tumbled into bed beside her best friend in Maddie’s room after a night out in the small college town.

Xana one of five roommates was still up after 4am having just ordered a food delivery for herself and Ethan.

Two other roommates, Bethany Funk, 23, and Dylan Mortensen, 24, were drowsily aware that something was wrong but survived, locking themselves in their rooms, terrified and confused in the dark.

The scene was one of utter chaos and Patterson said, ‘Kohberger panicked. I mean there is evidence of that. They have video of when he left after the murders, and he sped out of there.’

‘I think it was a combination of all these things and his life was about to get thrown up in the air. He was about to lose his fellowship and probably get thrown out of school. He was angry and he thought he could get away with it.’ Truth be told, Patterson said; he almost did.

Xana (pictured, right) one of five roommates was still up after 4am having just ordered a food delivery for herself and Ethan (pictured, left).

Surveillance footage from a neighbor’s security camera clearly shows a car, now known to be Kohberger’s white Hyundai Elantra, speeding out of the neighborhood around 4.20am. He is in such a rush that he nearly spins out on a corner.

And in his ‘panic’ – in the moments when, Patterson believes, Kohberger’s plan fell into disarray – the killer made a mistake and dropped the sheath for his Ka-Bar fixed blade knife.

Investigators found the blood-stained sheath underneath Maddie’s body.

It was DNA retrieved from the sheath snap and uploaded to a genealogical DNA database by the FBI that led them to Kohberger, who was arrested on December 29 – 47 days after the killings.

Patterson said, ‘I don’t think he made any other mistakes. Without that evidence I don’t think they could have brought this case to trial.’

On July 2 Kohberger accepted a plea deal in which he admitted his guilt in all five counts – four of felony murder and one of felony burglary – and waived any right to an appeal or the chance of parole.

Kohberger spoke only to acknowledge his guilt – in a performance Patterson watched and described as ‘incredibly dramatic and creepy.’

The hearing is a chance for friends and families to share the impact his crimes have had on them and memories of Maddie, Kaylee, Xana and Ethan.

But those hoping that Kohberger will shed more light on his heinous crimes are, Patterson believes, likely to be disappointed and the judge cannot compel the killer to speak.

Patterson said, ‘People tend to see the world in black and white. They want a clear answer.

‘I think we’ve made some sense of it all, but honestly if you asked Kohberger why he did it I’m not sure that he could really tell you.’