Police matched Bryan Kohberger’s DNA to a knife sheath found at the scene of a quadruple murder leading to his eventual arrest in Monroe County, according to an unsealed affidavit of probable cause.

Kohberger, accused in the November slayings of four University of Idaho students is back in Idaho, where he’s charged with four counts of first-degree murder and felony burglary.

Police said they recovered trash from Kohberger's parents' house in Albrightsville, and a lab later determined the DNA from the trash was the father of the person who left DNA on the knife sheath.

In the affidavit, police also allege that Kohberger walked right by another female student living in the home after allegedly killing Madison Mogen, 21; Kaylee Goncalves, 21; Xana Kernodle, 20; and Ethan Chapin, 20, on Nov. 13.

The female, identified in the documents by only her initials, D.M., told police she opened her door when she heard crying and ““saw a figure clad in black clothing and a mask that covered the person’s mouth and nose walking towards her.”

D.M. described the figure as 5' 10" or taller, male, not very muscular, but athletically built with bushy eyebrows,” the affidavit continues.

The female told police she locked herself in her bedroom after seeing the man.

Phone records, according to the affidavit, put Kohberger near the crime scene at least a dozen times before Nov. 13.

Police said they used surveillance cameras to match a white 2015 Hyundai Elantra seen on the Washington State University campus to the vehicle spotted around the crime scene on the night of the murders.

Kohberger was arrested at his parents’ home in eastern Pennsylvania last week and agreed to be extradited to Idaho.