Seems unlikely since LE was going around stores trying to discover who purchased such a knife recently.
It's possible that somewhere along the way some authority said "a KA-BAR type knife" which was morphed into "a KA-BAR knife". Unless there is proof we are as yet unaware of, I'd guess they are looking for a partially serrated edge knife with a blade stout enough to pierce or break bone, as opposed to say a kitchen/chef's knife which might instead be deflected by bone.
Unless one of the victims was a dedicated outdoors-type, the likelihood of one possessing a stout (thick bladed) knife is low.
So, IMO, it's then likely that the killer brought and left with the knife. Moo.
Hopefully there is undisclosed evidence that greatly narrows some unique characteristics of the weapon.
As a general resource, a noted author of several highly regarded books on knives, maintains a section of Bladeforums dedicated to identifying knives. His c.v. is at the link: Bernard Levine's Knife Collecting & Identification
Bladeforums is one of the best known forum on knives. The knowledge base is phenomenal. IMO.