I have been following the story every day. I am really intrigued by it.
It seems to be a student rented house for college students. So, according to many others, the house was a party house. It was rented to college students over the years. In fact, people would party in the home even when the renters were not there (current renters)--I guess tons of people would just come and go as they please, partying in the home, whether or not the renters were there. Which would lend to the idea that the killer knew the lay out of the home if he partied in it.
Also, they just interviewed a previous resident who said the house is very old and creaky and squeaky and you could hear anyone walking at night. The question then became, why didn't the two other students who lived in the home and survive hear anything? A logical explanation could be that they were passed out drunk or high.
I heard of the Keddie Cabin murders. Crazy how it's still unsolved, but so many cases go unsolved.
Well - I'm glad you said that and are up to date with the case. You know a lot more than I do but just goes to show: that house has had years of party type students in and out whom are familiar with the property. Like you said: parties constantly. Which brings us back to DNA/hair/fingerprint evidence: there's bound to be dozens upon dozens of samples collected. No wonder they're going slow through this. Don't forget that students aren't exactly known for being the cleanest types of people in terms of hygiene and maintenance. If it's anything like student digs I've partied in my life growing up: the landlords don't give a toss after previous tenants go in terms of repainting. The most they'll do is replace broken furniture/glass knowing full well the house is going to get trashed again. Could be fingerprints on the walls/windows that have been there for years. Could be talking 100's of different samples? ? ? ?
My next question is based on what you said about the floorboards being squeaky. I'm in the UK so am used to this as our houses are quite shoddily built.

Thing is: when I'm used to knowing which floorboards/areas of the floor are less 'noisy' than the others - I kind of know where to step and can make up up stairs/rooms/areas of my house without making noise whereas someone who doesn't know which bits to step on would make a lot more noise - if that makes sense?
Yeah it was probably noisy but what if this guy was so familiar with the property - maybe there's bits he could avoid being heard of? Maybe that's why the entrance the police said was on the 2nd floor not the ground? Or whatever - if that's true. But like I said maybe the killer knew EXACTLY where to step and how to position around the place to avoid the noisy boards?
So - that brings us back to maybe it's true and he didn't know these victims but he certainly knew the property VERY WELL - so it could be someone outside the circle of that group and possibly a previous student maybe 5-10 years older now and beginning his life as a killer? OR it could be someone they knew who has partied there a lot with them and knew the house - but that group *SHOULD* have been questioned/requestioned/questioned again by now and no arrest so maybe it's a shitbag from the group that USED to live there/party there years ago and the police are still casting that net in order to question those groups?