:wagon: :greetings: Thank you for offering your insight.
I don't feel a professional would have used a shotgun. These crimes were personal. Weapons used were familiar to the UnSub(s).
Initially, and currently, I felt it was a family member due to the lack of forced entry [at 3 of the 4 scenes, iirc]. However, I do not see the killer family member(s) walking up to the door and knocking, before being let inside, while holding a huge shotgun in their hands or else the bodies would be found just inside the doors. Yes?
I do think house keys were important to the UnSub(s). CRsr knew he was about to be shot, jmo. Some of his injuries seem to be defensive wounds since the extremities are involved. He turned his back on his killer in an attempt to get away and was shot in the back that shattered his vertebra, jmo based on AR.