Bryan Kohberger leaves after an extradition hearing at the Monroe County Courthouse in Stroudsburg

As details continue to emerge about University of Idaho murders suspect Bryan Kohberger, those who were closest to him are claiming he lost several friends over the years due to his inappropriate behavior and heroin addiction.

Kohberger, 28, was arrested on Dec. 30, 2022, for fatally stabbing college students, Kaylee Goncalves, 21; Madison Mogen, 21; Ethan Chapin, 20; and Xana Kernodle, 20, at an off-campus home in Moscow, Idaho.

Years before he was accused of committing the quadruple murders, Kohberger was friends with Thomas Arntz, 27, who met him in their early teens while living in Monroe County, Pennsylvania.

However, Arntz told the Idaho Statesman their friendship ended after Kohberger crossed the line. At the time, Arntz was grieving the death of his aunt, and Kohberger had a habit of playing relentless mind games.

"It almost seemed to me he had a desire to be the alpha," Arntz said. "For no reason, he'd try to grapple me and put me in headlocks when I didn't want to. He tried to portray it as just boys being boys, but that's not the way I ever took it."

Although Arntz told Kohberger he wasn't interested in his psychological games, the suspected killer refused to ease up on the manipulation. ​​"He always wanted to be dominant physically and intellectually," Arntz recalled.

"He had to show that he was smarter and bigger than you, and try to put me down and make me feel insecure about myself. So much of that was a torment, and I didn't want to be around him anymore."

Years after ending their friendship, Arntz enlisted in the U.S. Army and was contacted by Kohberger on social media. In the Facebook message, Kohberger congratulated Arntz and apologized for his behavior when they were younger. However, Arntz said he didn't reply to the message.

Arntz wasn't the only person who had a falling out with Kohberger. Jack Baylis reportedly ended his friendship with the murder suspect after learning about Kohberger's heroin use.

"I think drugs goofed him pretty bad. He was having a time. He'd tell me, 'I'm clean now, I'm totally clean now,' and he'd have bleeding track marks" on his arms.

Kohberger's drug issues also ruined his relationship with Casey Arntz, the older sister of Thomas Arntz. Casey Arntz reportedly learned Kohberger tricked her into driving him to buy heroin and needles under the guise of running errands.

"He literally used me to get it," she said. "I was freaking out and not happy I had heroin in my car and didn't even know."

When Casey Arntz later confronted Kohberger through a Facebook message, Kohberger apologized and said he was in rehab. "Honestly, I don't want to hear it," Casey Arntz replied.

Kohberger faces one count of felony burglary and four counts of first-degree murder in the deaths of the four University of Idaho students. Kohberger's next court date is scheduled for June 26.