One of the survivors of the University of Idaho murders didn't call police after coming face-to-face with the suspect because she was "paralysed by fear", it is claimed.
The bodies of students Kaylee Goncalves, 21, Madison Mogen, 21, Ethan Chapin, 20, and Xana Kernodle, 20, were found stabbed to death in their beds.
Suspect Bryan Kohberger, 28, a criminology PhD student at Washington State University, allegedly came into contact with a roommate before she locked herself in her bedroom, according to his affidavit.
It is believed the roommate saw Kohberger just before 4.20am on November 13 after he allegedly killed her roommates.
She heard someone crying from Kernodle's room which is when she opened her bedroom door and saw the suspect looking directly at her.
Two New York cops stabbed during celebrations in Times SquareAccording to Kohberger's affidavit: "[The roommate] saw a figure clad in black clothing and a mask that covered the person's mouth and nose walking towards her.
"The male walked past [the roommate] as she stood in a ‘frozen shock phase.’"
Dr. Katherine Kuhlman, a police and public safety psychologist in Arizona, believes the girl would have experienced "fight, flight or freeze" emotions when she encountered the suspect.
She told Fox News: "When a person goes through trauma, they are going to experience fight, flight or freeze.
"Most people in their entire lives won't have to deal with this type of trauma and won't mentally prepare for it."
The roommate told police the suspect had "bushy eyebrows" and walked past her as he left through the sliding glass doors on the second floor.
She woke up at 4am by a noise which she thought was Goncalves playing with her dog but heard her say "there's someone here", according to the affidavit.
As the suspect left it wasn't until nearly eight hours later that one of the roommates contacted 911 after reporting an unconscious person at the scene.
Cops have not revealed who placed the call.
Dr Kuhlman believes the roommate would not have identified the clues that she was in a crisis situation.
At least nine killed after New Year's Day stampede at shopping centreShe said: "Trauma becomes more difficult to process when it's something that is so far outside of our consciousness, it doesn't seem to make sense to us.
"In this case, no one ever thinks they're going to have this man come into their home and brutally stab their roommates."
Mary Ellen O'Toole, a retired FBI behavioural profiler, said the roommates instinct to go back into her room and lock herself in "probably saved her life."
She believes if the roommate went to upstairs to see what was happening she could have been the fifth victim.
She added: "She was probably scared beyond belief. She chose to hide in her room, and it probably saved her life."
As the attack happened the other surviving roommate slept through the brutal murders.