I have a question related to getting inside his head as to why did this happen / what was he thinking.
Was he not worried at all that someone in the house might have a gun for self defense?
Don’t bring a knife to a gun fight, etc.
The knife is such a strange element of choice - very personal and also very risky in so many ways.
Thoughts?
The close contact required with stabbings could mean more rage, experts say.
Knife vs. Gun: What a Weapon Reveals
But why a knife?
"Anytime somebody commits a murder or assault, either by choking, stabbing or making bodily contact, it always speaks to a level of rage and perhaps a personal connection to the victim that shooting with a gun does not," said Naftali Berrill, a forensic psychologist in New York City.
"When you are stabbing someone, it's close and in your face. The experience is more visceral and more graphic, more provocative. It speaks emotionality, whether rage or paranoia."
The close contact required with stabbings could mean more rage, experts say.
www.seeker.com
Other considerations;
My firearms are purchased through a firearm dealer, with a background check, and they have a s/n on them.
When a round is fired, indentions are made, on the brass. These indentions are much like fingerprints and can be traced back to a firearm, or a type of firearm. If BK was found to have ever had the same firearm he could be connected via the firearm's "fingerprints". There's that pesky problem of finding expelled brass in the dark too, b/c it will have a signature as well (unless he uses a revolver, then reloading may be a problem).
There's also sound in such a tight, close quarter, neighborhood. I'd guess shots heard, in a small college town, are not very common (Unlike here, I hear them frequently, and don't think twice). He'd probably have thoughts about a silencer. If so, he'd have to order a silencer which would leave a paper trail, through the government. A wait for the approval and pick it up at an approved firearms dealer. He could build one himself, so as not to leave a paper trail, but somehow I don't see him as a builder. Thus, the knife. It's possible he's had it for quite a while since he once had dreams of becoming an Army Ranger.
Pure speculation.