I've wondered, if perhaps KR was murdered simply b/c he'd driven by, maybe as they were leaving one of the properties, and they couldn't take the chance he'd seen them. It's also been bandied about that he stopped at CR1's most morning before heading to work. If so, that would have to have been very early in the a.m. He'd have to be taken out, based only on that reason, IF, in fact, that was his daily habit.
I believe all the doors were locked, the pits were outside, etc... to keep the one person who came by CR1's later each morning, BJM, from finding the bodies so early. It didn't work, but I believe that was part of the reason.
If my bil's car was in the drive, his dogs were outside, etc... I'd think, well, he's home, he doesn't need me to care for the animals or the plants. Now, I'm not as close w/my bil as BJM was with the Rs, so they probably underestimated her desire to know why he was home (was he sick, did he need help, the dogs were not usually out so that was off, etc... as she was there every single day, unlike me, who sees my bil 2-3 times a year). Just rambling thoughts.