Former FBI Agent Shares Theory Why Roommates Were Spared in Idaho Murders

In the November killings of four college students in Moscow, Idaho, the surviving roommates may have been spared because the assailant ran out of "energy," according to a former federal agent.

Tracy Walder, who worked as staff operations officer at the CIA as well as an agent at the FBI's Los Angeles office, dissected the slayings with NewsNation on Thursday after Idaho police released the probable cause affidavit that led to Bryan Kohberger's arrest.

Kohberger, a 28-year-old Ph.D. student in the criminology department at Washington State University, was arrested December 30 over the November 13 deaths of Kaylee Goncalves, 21, Madison Mogen, 21, Ethan Chapin, 20, and Xana Kernodle, 20. The four were slain in the women's off-campus house near the University of Idaho. Kohberger is charged with four first-degree murder counts and one count of felony burglary.

According to the police affidavit, one of the two surviving roommates, Dylan Mortensen, encountered the attacker on the night of the killings. Mortensen reportedly told investigators that she had opened her bedroom door multiple times after hearing crying coming from the other rooms.

After opening her bedroom door for a third time, Mortensen saw a "figure clad in black clothing" walk past her and out of the house's back sliding glass doors, police said.

Walder told NewsNation that the killer could have left Mortensen and another roommate alive because of the amount of energy expended in fatally stabbing four people.

"When you stab four people, that takes a lot of energy and a lot of exertion," Walder said, adding that she thought fatigue played a role in the attacker's departure from the house.

"Personally, based on the evidence that was released in this probable cause affidavit, I'm not certain that [the assailant] planned on killing all four of them or expected all four of them to be there," Walder continued. "So I think that [the assailant] may have been in such a daze and such a state that [they] just walked right by that roommate and didn't necessarily see her."

Police said the suspect also spared one of the victim's dogs after encountering it in the house. Mortensen told investigators she could hear the dog barking during the night of the killings.

Walder also discussed Mortensen's "state of shock" that she described feeling, which the former federal agent said can take hours to "wear off." According to the police affidavit, a call was made to Idaho police several hours after the assailant was seen by Mortensen in the house.

"I know a lot of folks are sort of upset with her for not calling the police," Walder added. "But it's really hard to put yourself in a situation like that, and I'm not sure at the top of her mind she had thought that four of her roommates had been murdered."

The former federal agent also told Newsweek in an email Friday that it's possible the attacker entered Mogen's room first upon breaking into the house, given where investigators found a knife sheath that police said had DNA evidence linked to Kohberger.

"Again this is just my hypothesis, it appears since the sheath was left in Maddy's room, perhaps she and Kaylee were murdered first," Walder said. "This means [the killer] walked upstairs first."

According to the affidavit, Mortensen's bedroom was on a floor below the four victims' rooms.

Kohberger appeared in magistrate court in Latah County, Idaho, on Thursday morning and is scheduled back in court January 12.

Update 1/6/22, 4:04 p.m. ET: This story has been updated with additional comment from Walder.