In a significant development in the investigation of the University of Idaho quadruple homicide, the Idaho State Police have unveiled images of a Ka-Bar knife sheath. This crucial piece of evidence, left behind by suspect Bryan Kohberger, played a pivotal role in his arrest during the extensive inquiry into the tragic deaths of four undergraduate students at an off-campus residence.

The photographs were part of a comprehensive public records release, which included over 2,300 pages compiled by state investigators.

Among the released materials were handwritten notes from investigators, images of nail clippings from the victims analyzed for DNA, and samples from Kohberger’s Hyundai Elantra, which underwent testing at a crime lab.

An image provided by Idaho State Police displays the Ka-Bar knife sheath, which is thought to have contained the weapon used by Bryan Kohberger in the 2022 murders of four University of Idaho students. (Moscow Police Department)

Another photo from the Idaho State Police shows the Ka-Bar knife sheath, believed to be used by Kohberger in the tragic event. (Moscow Police Department)

Forensic experts examined the sheath for DNA, successfully obtaining a sample from its snap, which contributed to the ongoing investigation.

The sample later turned into a tip developed by investigative genetic genealogists and ultimately led police to Kohberger’s parents’ home in Albrightsville, Pennsylvania, where he was arrested on Dec. 30, 2022.

An evidence photo supplied by Idaho State Police shows a pair of Radians-branded gloves retrieved from Bryan Kohberger’s parents’ home in Albrightsville, Pennsylvania. (Moscow Police Department)

He pleaded guilty in July and was sentenced to four consecutive prison terms of life without parole, plus another 10 years, for the murders of Madison Mogen, 21, Kaylee Goncalves, 21, Xana Kernodle, 20, and Ethan Chapin, 20.

Madison Mogen, top left, smiles on the shoulders of her best friend, Kaylee Goncalves, as they pose with Ethan Chapin, Xana Kernodle, and two other housemates in Goncalves’ final Instagram post, shared the day before the four students were stabbed to death. (@kayleegoncalves/Instagram)

According to the investigators’ notes, the victims left a sliding door open on the night of the attack for Goncalves’ dog, who was found unharmed in her bed. Goncalves and Mogen were both killed in Mogen’s bedroom.

Many of the records had to do with crime lab work, including DNA testing, fingerprint analysis and other measures early in the investigation.

This is a developing story. Check back with Fox News Digital for updates.