That was a good list you made, PT1960. I assume that motive #3 was monetary gain by the spouse/ex-spouse. I thought of another reason:
5) Property/money dispute with someone, i.e. it could be a neighbor, a "friend," or a business associate, etc.
My vote is for #1. We know the son wasn’t home. We know he was going to school in UT, not CA where his mother lived. We don’t know why but since it’s more common than not that parents want custody of their kids, it’s not unlikely the ex-wife wanted custody of her son. Or at least for him to be close enough to visit.
We know the husband wasn’t killed, but was seriously injured. If he was a participant it’s unlikely he would allow himself to be hurt so severely. If the ex-wife wanted his new spouse dead she might want him dead too, or she might not want her son to lose his father. Either way, I think he was shot accidentally or it was a kill shot that failed.
Shotgun is a sloppy weapon. Doubtful the shooter was an experienced assassin. IMO more likely “someone” paid or sweet-talked some idiot into taking out one or both of the victims.
Almost immediately after the murder LE announced their was no danger to the community. So they don’t think it was a local crazy on a rampage. A randomly hired gun toting idiot would likely be harder to catch than than someone who’s a known local criminal or involved in a business deal gone bad. And there’s no indication law enforcement has made any progress at all. None. I continue to be amazed at the apparent lack of effort by local LE and lack of interest by the local media. And suspect LE thinks they know who did it but don’t believe they’ll ever be able to prove it unless/until someone spills the beans.
It makes sense someone whose wife was gunned down in their house in a town that wasn’t a long-term home would choose to leave that town. And return “home”. In this case to CA. Whether she was involved or not, It appears the ex-wife may well have gotten what she wanted.
My opinion only based on very limited info.
Does anyone know what current custody arrangements for the boy look like?