Cops are still “puzzled” about why a surviving roommate in the University of Idaho quadruple murder waited eight hours after the slaughter to call police, an Idaho law enforcement source told The Post.

Dylan Mortensen, 21, opened her bedroom door to see an unknown “figure clad in black clothing and a mask” walking past her, towards the home’s back exit, just after 4 a.m. on Nov. 13, she told investigators.

Yet neither she nor the other spared roommate, Bethany Funke, 21, called police until noon.

The 8-hour gap “has been something that we have puzzled over — we don’t know if it was an issue of intoxication, or of fear,” the lawman said. 

According to a newly released police affidavit, in the moments before Kaylee Goncalves, Madison Mogen, Xana Kernodle and Ethan Chapin were stabbed to death on the two upper floors of the Moscow house, Mortensen thought she heard Goncalves saying, “There’s someone here,” followed by the sound of crying from Kernodle’s room and a male voice ringing out, “It’s ok, I’m going to help you.”

Early police reports said that Funke and Mortensen, who lived on the first and second floors of the house, recruited friends to the scene before one of them finally called 911 at 11:58 a.m. The pair were quickly ruled out as suspects and have cooperated with the investigation, cops have said. 

Despite the baffling delay, cops on the case “are really, really confident about it not being an issue of [Mortensen] being involved,” the source said. 

“We look at these things through the lens of rational adults — and when we do that, sometimes things don’t make sense to us — but she’s a 20-year-old girl and we don’t know what she was doing, or if she was scared,” he continued. 

Law enforcement is also currently coming up empty in their search for connections between the six students and the accused killer, 28-year-old Bryan Kohberger, who lived a 15 minute-drive away in Pullman, Wash., where he was a PhD student studying criminology.

“There’s no rhyme or reason to it — there are no ties between them,” the source said. “Nobody has said ‘we’ve found the link’ — and that would include Dylan.”

Kohberger was arrested on Dec. 30 in his parents’ home in Albrightsville, PA. He and his dad had driven cross country in Kohberger’s Hyundai Elantra, which had been spotted near the killing scene on the night of the murders.

One expert said the 8-hour delay likely made no difference in lives lost.

“The four were dead when the guy left, and they weren’t crying for help, they weren’t moving or trying to get out,” said Dr. Michael Baden, former chief medical examiner of New York City, adding, “They weren’t in a condition where an ambulance could save their life, on the basis of what we know now.”

“People are concerned about [the delay in calling for help], but it isn’t a concern from a forensic point of view. Nothing was interfered with by that delay,” Baden stated.