I was long thinking about a potential scenario. Supposedly, BK was driving to Moscow for drugs, or drugs and dating someone? In the area of the party house and frats there probably quite active business. In this situation, switching off the phone is not unlikely. I don’t know what happens, but whatever it is, it renders BK comatose for a while. BK doesn’t know the inhabitants of the house, but the other person does, and has a beef with someone there. An ideal moment - he parks the car next to the house, takes BK’s knife, enters the house, kills whoever he planned to, and maybe, KG as the side victim. Leaves the sheath. Then takes the car with very sleepy BK, drives him around for two hours till he BK up, then brings him back and says, “you made a mess there this night”, I’ll drive you home. BK doesn’t remember what happened, so he accepts the “help” of his “friend”. Next day, he reads about the murders. He tries to get in touch with his “friend”, but that one is less responsive and ultimately, disappears. BK basically has amnesia for that night. Two front seats of Elantra need to be checked for DNA, not BK’s but someone unrelated to him but known in Moscow.
This scenario is lax, but at least considers that the killer had a motive, and targets. BK doesn’t seem to have either.