More than a week after the murders of four University of Idaho students, the suspect remains on the loose as police continue their investigations. Now, experts are considering clues – like the knife likely used to kill all four individuals – that may help identify a suspect.

Jonathan Gilliam, a former FBI special agent and Navy SEAL, said the suspect’s use of a Ka-Bar knife, also known as a "Rambo"-style knife, could point law enforcement in the right direction. 

"That knife is pretty much a relic," Gilliam said on "Fox & Friends First" Monday. "Nobody really uses that knife except for people that had them when they got out of the military or they got handed down."

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Ka-Bar knife inset in front of house where students were murdered.

Police suspect a KaBar knife may have been used in slayings of four University Idaho students, inset. Caution tape surrounds the house near campus where the students were slaughtered. (Credit: Ka-Bar / Derek Shook for Fox News Digital)

He told co-hosts Ashley Strohmier and Todd Piro that the knife could be an important part of the investigation. 

"If they have ROTC at that school, that could be something that ROTC would have," he explained.

Gilliam noted that the University of Idaho had also issued a "Vandal Alert" to staff and students in September with the subject line "Threat with Knife." 

"This is something that they need to be looking at because the potential that this person could be a student, could be ROTC, could be somebody that lives in the area, kind of seems a little bit more significant," he said. 

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A split photo of the deceased students.

University of Idaho students Ethan Chapin, 20; Xana Kernodle, 20; Madison Mogen, 21; and Kaylee Goncalves, 21.  (Jazzmin Kernodle via AP/Instagram/ @kayleegoncalves)

Gilliam, after reviewing the details of the murders, said he believes it's more likely that the killer is a man. 

"It takes a lot of strength, you'd be surprised, to continue to stab multiple targets with this ferocity," he said.

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He said the suspect was likely either someone who had access to the house or was someone who watched the residence and waited for everyone to "shut down" for the night. 

"I think this is where investigators are going to start looking," he said.