All JMO…
I don’t think BK had any specific connection to any of the occupants of 1122 King Rd, but nor do I believe he just happened upon the house that fateful night/morning.
I think he had been watching them…whether he saw the house as an easy target or whether he took a shine to one of the girls, I don’t know, but he chose the house for a reason and this is what interests me. Whilst the house being an easy target is possible, I suspect that perhaps he had in fact been stalking one of the victims and was obsessed with her, although a stalker has never been confirmed so this is MOO.
I think he was obsessed with what drove people to commit murder as part of his studies, this then turned into a further obsession over how it feels to actually do it, and he became so obsessed with it that he wanted to know for himself. Research wasn’t enough. He developed an urge to kill, he just needed a victim.
Why the girls? Perhaps he was a loner growing up, perhaps he wasn’t successful with girls, perhaps he resented them and had incel vibes and felt they deserved it, or perhaps he had never been up close and personal with young, attractive women before and this was his opportunity.
I think his burning desire to know what killing someone felt like just completely took over his mind, rendering his knowledge in his field useless. He was sloppy (DNA and Elantra identification) when he should have known better. He didn’t plan well enough and got caught over something that he could have prevented, all because his desires caused him to lose control.
With regard to his poor planning, I also don’t believe that he intended on killing so many people. Perhaps one, maybe two? I think the others heard a noise and ended up as collateral damage. Ethan included.
All MOO.