Boxing coach Jesse Harris remembers the day a concerned father brought his shy 15-year-old son into his Pennsylvania gym.
'He was kind of quiet... I guess he was having some discipline issues, and he was overweight, so he had a lack of confidence,' Harris told the Daily Mail.
For Harris, it was a classic case of a teenager who was in need of a healthy outlet and some extra guidance to keep in line.
He didn't see any warning signs of how the boy would turn out 15 years later: a mass murderer who stabbed four college students to death in their sleep.
Last week, Bryan Kohberger, now 30, confessed to the murders of Madison Mogen, Kaylee Goncalves, Xana Kernodle and Ethan Chapin in Moscow, Idaho, on November 13, 2022.
Kohberger - who was living in Pullman, Washington, as a criminology PhD student at Washington State University at the time - broke into an off-campus student home and slaughtered the victims in a 13-minute rampage.
His motive for the crime remains a mystery. He had no known connection to the victims or their two surviving roommates Bethany Funke and Dylan Mortensen.
Now, in the absence of any answers, people from Kohberger's past are left searching for clues as to what went wrong.
Speaking out for the first time in an exclusive interview with Daily Mail, Harris said a teenage Kohberger seemed no different to many of the kids who have walked through his doors over the years.
Kohberger's father Michael Kohberger had brought him to the boxing gym in Brodheadsville - in the Poconos region of Pennsylvania where the killer grew up - to help with issues around his weight, confidence and discipline.
Though Michael, now 70, never went into detail about what problems Kohberger was having, Harris got the sense he needed some support in guiding his son.
'His dad was a little older when he had him. So it's what I call a young lion, old lion mentality,' he said.
'I have sons of my own and when they reach a certain age, they want to take on the lion, the head lion, and I think that was something that was starting to happen.
'I think Bryan began to show his size... and his dad was an older gentleman. He wasn’t going to be rolling around out in the grass with his son.
'So I think that that was something that he needed help with, trying to keep him in line.
'And I think that’s where we came into play as well. But [there’s] no situation that I can think of that we had to.'
He added: 'His dad needed another avenue and another support that he could kind of help guide him.'
Harris, known as 'Coach' to his students, said it was also about helping Kohberger - who childhood friends have previously said was bullied because of his weight - lose weight and gain confidence.
'I think it was more or less to find some place where he could interact with other people and not feel insecure,' he said.
Bryan Kohberger in court on July 2 where he pleaded guilty to the murders of four Idaho students
'So his dad brought him to the gym to try to get him moving and doing some things to keep him healthy,' he added.
Harris explained his boxing program wasn't so much about physical combat but about coaching kids and giving them 'the discipline of working hard towards something, working collaboratively with other people, teaching them teamwork, things of that nature.'
'We got a lot of kids that were having some social issues or issues with their parents,' he said.
'So one of the things we used to enforce was, in order for you to be a participant at my gym, there are some things you have to maintain: homework, grades in school, being disciplined at home. So those are the things that I enforce.'
Some kids would be recommended through social workers to join Harris's program while others would join because they 'didn't quite fit in on the basketball team or the cheerleaders or the football team.'
Harris made sure all the kids knew his door was always open if they needed someone to talk to.
'I would tell the child in front of the parent, if you need to talk to me and you can't talk to your parents, give Coach a call as my door's always open,' he said.
Kohberger began coming to the gym most days after school and worked hard, throwing himself into training. Michael would usually bring his son and stay while he trained, Harris said.
He was accepted by others at the gym and became more comfortable working out with others, he added.
'You got in the gym and you became part of the family if you earned it,' Harris said.
Over time, Kohberger lost weight and his confidence began to grow.
'I kind of realized, 'man, you're losing weight. You're looking good.' He was very proud of himself. I saw a little change in his personality when he lost the weight - he was proud of himself,' Harris revealed.
During his time at the gym, Harris said he never noticed any red flags or a dark side to the teenager.
'I wouldn't say he was an antisocial person, but he wasn't the one cracking jokes either,' he recalled.
Some of his school classmates attended the gym and Harris recalls Kohberger would talk to them.
There was also nothing unusual about his interactions with other people - in particular the girls and women training there.
'I never saw and no one ever said anything to me if he said anything out of line, or that he would have an aggressive personality towards [females]. Not at all. We had young ladies in the class that were very serious athletes, so it wasn’t really set up for socializing. But I don’t recall anyone ever saying, ‘you said something to me, I felt uncomfortable,’
After about two years, Kohberger stopped training at the gym.
Harris only recalls seeing him once after that when Michael - who worked in HVAC - did some work for him and Kohberger helped his father out.
The coach said he was 'alarmed' to learn years later - following Kohberger's arrest - that he got involved in drugs and became a heroin addict, losing more than 100 pounds.
He went to rehab multiple times and, in 2014, the then-19-year-old stole his sister's cell phone and sold it for money for drugs.
Court records previously seen by ABC News show Michael called the police over the theft and his son was arrested.
He didn't serve any jail time and there is no public record of the arrest - due to Monroe County's program wiping records for some first-time offenders.
Kohberger later got clean and appeared to get a new focus: studying criminals.
First, he went to DeSales University earning a degree in psychology and a Masters in criminal justice under renowned serial killer expert Dr. Katherine Ramsland.
He then moved 2,500 miles across the country to enroll at WSU in the summer of 2022.
That December - while the small college town of Moscow reeled from the shocking murders - Kohberger returned to his parents' home in Albrightsville, Pennsylvania, to spend the holidays with his parents and two older sisters.
It was there - in the family's gated community in the Poconos Mountains - that he was arrested on December 30, 2022, over the quadruple homicide.
Harris was 'shocked' when he saw the news of Kohberger's arrest.
He reached out to Michael.
'When I saw the news I texted his dad to tell him, 'I saw the news and my heart goes out to you and the family and if there's anything I can do please let me know.' And that was it,' he said.
Harris said he didn't get a response. But, he said Kohberger’s attorneys - who subpoenaed him to testify as a witness in his capital murder trial - later told him Michael had been happy he had lended his support.
'Any parent that has children - whether they're yours or not - as a parent would hate to think that their child can do something like that. So I think I was feeling more like a parent,' he said.
'But I also felt the feelings of a parent that got your children taken away from them,'
he said of the victims’ families.
Over the next two-and-a-half years, Harris said he avoided following the case - and didn't really know what to make of Kohberger's innocence or guilt.
'I didn't really cast a feeling on whether he was innocent or guilty. So I think that's why I was so disappointed when I found that he was,'
he said.
That all changed on July 2, when Kohberger finally confessed and changed his plea to guilty.
Under the plea agreement, Kohberger avoids the death penalty. He will be sentenced to life without parole and will lose his right to ever appeal.
'When he admitted to doing it, I was very hurt,' Harris said.
'And it's strange because I didn't think that I would feel that way, but I felt that. I was a little confused... I felt very disappointed and very hurt.'
For Harris, a lot of the children he has coached have gone on to successful lives and careers including in real estate, law and military and still call up 'Coach' to check in with him.
Looking back, he has racked his brain searching for any warning signs or red flags that might have indicated what Kohberger would become.
He can't find any.
'I really gave that a lot of thought... but no, I didn't see anything of the sort that would make me think he could be guilty of anything of his magnitude,'
he said.
Harris wondered: 'He was constantly challenging himself to achieve different things... I don't know all the details but I just kind of think it was just another thing that Bryan was trying to achieve.'
He now thinks about what he would say to the mass killer who, as an overweight, unconfident teen, he had tried to offer coaching and guidance to.
'If I had a chance to talk to him, I would sit down with him one-on-one and just try to get an understanding of 'what was happening at that moment in your life?'