MOSCOW, Idaho - Warning: The following contains details that might be considered graphic in nature.
The fixed-blade, Ka-Bar-style knife police are reportedly searching for in connection with the violent murders of four University of Idaho students is known to dull quickly and would have likely caused injury to the attacker because of the physical force required, an expert told Fox News Digital.
Police have said since early in the investigation that they are looking for a "fixed-blade knife" that was believed to have been used in the Nov. 13 quadruple homicide. The Idaho Statesman spoke to a Moscow Building Supply store manager earlier this month who said police had asked if the business sold Ka-Bar knives. The store does not sell them.
Jonathan Gilliam, a former FBI special agent and law enforcement officer, told Fox News Digital the type of knife involved in the crime sheds light on the way in which the attack could have progressed.
Gilliam, also a former U.S. Navy SEAL, said he personally has experience with Ka-Bar knives, which he said dull quickly and are often used for survival-centric activities, such as skinning the bark off a tree, digging a hole or cutting leather.
"It’s not going to be as thin and able to slice" as other knives, he said. "And when you do get it sharp, it’s going to dull again just because of the nature of the fact that it’s kind of a fat blade."
The tip of the knife, he said, is known to break off. Ka-Bar knives are more frequently used for cuts that involve thrusting motions, instead of smoother motions, Gilliam further explained.
"A thrusting is much more a physical activity," he added. "And so, the more you do that, the more tired you're going to be."
Gilliam added that he expected that the killer would have shown signs of bruising or cuts on the underside of his or her hand.
And as the blade gets duller, it also becomes more slippery, he said.
"It’s a tremendous amount of effort that you are knowingly putting out for the purpose of killing," he said
Gilliam told Dr. Phil Monday that investigators would likely see "a progression of smaller and smaller wounds" on the victims as the killer carried out the attack, which likely grew more physical with each person.
Tuesday marked one month since Ethan Chapin and Xana Kernodle, both 20, and 21-year-olds Kaylee Goncalves and Madison Mogen were discovered fatally stabbed inside the girls’ off-campus home.
The victims’ bodies were discovered just before noon on Nov. 13. The home at 1122 King Road is located just one block from the University of Idaho campus and near some fraternity houses.
Officials have said they believe the victims were asleep when they were attacked between 3 a.m. and 4 a.m. Each victim suffered several stab wounds, and some showed signs of trying to defend themselves.
The homicides were carried out on the second and third floors. Two other roommates were on the bottom floor of the home and were unharmed, police said.
Moscow Police officers responded around 11:58 a.m. to a report of an "unconscious person" at the address, but several people had gathered at the crime scene by the time police had arrived, officials said.
The 911 call "originated from inside the residence" and came from one of the surviving roommates' cellphones, police said. Multiple people allegedly spoke to the dispatcher before officers arrived.
Police are analyzing 113 pieces of physical evidence and about 4,000 photos from the scene. They have also received more than 2,645 emails and over 2,770 calls to the City of Moscow tipline, police said. The FBI has received more than 1,084 digital media submissions.
Last week, police revealed they had received tips and leads about a white 2011 to 2013 Hyundai Elantra spotted near the crime scene in the early morning hours of Nov. 13. They are seeking to speak with the person or people who were inside the vehicle and are asking the public for any information.
The Moscow Police Department is urging the public to submit any images or information considered important or useful to their investigation. The public can do so by calling 208-883-7180, submitting tips through email@example.com or sending digital media here.