I think they planned the murders for the dates they occurred on.
I don't have evidence for that, but it does seem like they had specific plans each time they murdered.
OTOH, I can't wrap my head around the cold evening that Alex attempted to shoot Tammy with an AR15. Even with a silencer, what was the plan?
Was Chad going to pretend not to notice his wife dead in the driveway for a few hours? Pretend he fell asleep then call 911 with his fake crying act in the morning? Or make Emma or Garth find her?
Joe Murray did hear the hoopla. So assuming a successful hit and a quick 911 call, how far could Alex have run? Was he going to run into the house and hide there, while Chad pointed south or something?
All that came to mind in considering the Yellowstone murder theory. For some reason, I don't think there was a murder plan there. They do seem to murder on their owned or rented properties. But, they also have experienced failed attempts. So who knows?
MOO