At first, it looked like someone had a beef w/ CR1 & DR and took out their entire family, but GR was in the wrong place at the wrong time. Then, they discovered KR, and that changed the whole dynamic for me. KR didn't do it and commit suicide. That's been established. I think CR1 was at the top, then KR, then GR. I'm sure FR knew about the marijuana and helped w/it. BJM had to be privy to everything too. (Yet, she wasn't murdered.) They all knew, (unless those four kept the grow op locked down and no others w/access), but those four were the main ones working with it, (and I'm thinking BJM had some hands on with it). What could one, or all, of those four, have done to someone, to bring this upon their entire family? Revenge? If it's a revenge killing, about a 1/3 of all these type killings (mass) are family related.* The assailant is most often male. They blame their family for their lack of success/happiness. Have access to weapons, are usually a loner type, likely to have a mental illness, and have probably planned this for quite some time.
I'm still not in the BJM &/or DS did it camp, but, in theory, they are the two family members whose planned activities changed. BJM usually got there earlier, IIRC, and it was not normal to bring two other people w/her. DS was supposed to spend the night w/KR but said he decided to go home (what time?), but then did not show up at 5:30**, when he said KR normally got up to work on/go to auctions, to go help him, as they'd planned.
*The other two most common mass killings is 1) co-worker related and 2) blames society and kills random people.
** The time that it's been noted that shots were heard in that area.