IMO, there’s more to the story. Think of personal reasons: money, love, greed, sex, jealousy, broken heart etc. It’s been said all along that the killing was personal and that the killer was someone who was really angry. I’m guessing that the killer was pissed at X, killed E, K and M out of spite. I also think that BK knew X and possibly her sis. It was no coincidence that he ended up at WSU where Xs sis just happens to attend? I think BK may have had a previous online “ relationship”, “infatuation” with X - and she broke it off having been influenced and motivated by M and K because it was likely an unhealthy relationship. X found E and was happy with him and BK held a grudge. I get the impression that BK might be an uptight, controlling guy. He moved to Pullman and started keeping tabs on X. That’s the only thing that I can think of. I also think that X may have known BK for a long time before the killings. Just JMO. I don’t see any other connection. The medias obsession with K and M was stoked to direct the onus of the investigation away from the true targets X and E, while LE diligently tried to figure out their somewhat unknown timeline of Nov 12th. From BKs perspective, he probably felt like he was “ ganged up on” and given no choice about the break up. This had to sting especially if this was the only and/or first time that BK fell anything like love.