So we have either:
1) random skell / druggy wandering into a house opportunistically and up the stairs
2) professional hit hired by someone with a grudge or financial incentive
3) jealous plotting friend/relative/little brother, someone local and unstable but in their extended social circle
Place your bets, 1, 2 or 3?
I think #3 is most likely, but I’m not as quick to rule out #1 as others here, just because of local news stories I’ve seen of home invasions that have resulted in murders.
For example, there was this case:
Wife of famed music executive Clarence Avant killed in apparent Beverly Hills home invasion
The victim was an 81 year old woman. How much could she have really derailed their plans? There was no reports of items missing, though there was forced entry. (If memory serves, they caught this guy because he later went to break into another house in a different nearby city, and accidentally literally shot himself in the foot.)
And here,
"American Idol" executive Robin Kaye and her husband shot and killed at Encino home, suspect arrested, police say,
A couple was murdered by a random man who broke in, with no signs of forced entry. Reports don’t mention whether anything was taken. Subsequent news reports revealed the couple was shot with their own gun, the shooter called the police on himself and that’s how they located him, and he was found mentally incompetent to stand trial.
The only thing that distinguishes these cases for me really is that the police described them as possible home invasions (though, that’s not an insignificant distinction).
Then there was this older case, which was not a home invasion, but was ultimately determined by the police to be a “robbery gone wrong,” even though the “robber” didn’t bother to take the victim’s purse that was sitting beside her (suspect committed suicide, so no trial).
SHOCKER! Oscar Publicist Ronni Chasen Shot And Killed In Beverly Hills Driving Back From 'Burlesque' Premiere In Hollywood
(That said, while I’m generally not a conspiracy theorist, I have a conspiracy theory on that case, so I don’t personally believe the robbery motive. I recall reading a funny comment at the time from someone saying that if they are ever murdered in Beverly Hills, to please drag their body across the border into Los Angeles. While the BHPD are really great at what they do, murder investigations are not something they generally do, because not many people get murdered in Beverly Hills.)