[SteveH]

That’s imho a variation of (7) (murder by Brian directly in person), but ya, and ya, it might be the most likely scenario given what we currently know (mane not everything at least not yet).

It would be nice to have the complete details of the coroner report (etc).

And there must be many such homicides that we never hear of in the media... for whatever reasons... :-/

[SteveH]

https://www.npr.org/2021/09/21/1039268981/media-petito-like-racism-native-americans

[House Atreides]

“… And there must be many such homicides that we never hear of in the media... for whatever reasons... :-/…”
**********************************************************************
One good reason would be the non-typical and completely reprehensible behavior of the near-certain murderer’s family… the whole damn family!