RSBM
I don't think that's the only possible scenario for this crime.
So many cases on Websleuths, and in real life, are the result of the baffling behaviour of losers with guns, who have decided to make their mark on the world by killing someone or some people. It makes no sense, it's not rationale, it's not in their own interest. It seems, the less power and resources they have, the more likely they are to kill.
Some of them are suicidal or nuts, like the numerous high school, etc shooters, and don't mind dying in the process. Some do care about getting caught, and plan the crime to avoid it.
I think the thrill is definitely part of it: getting it right, mission accomplished, getting away with it.
I could go into lots of examples, but I'll just cite the first well known one, the
Clutter family massacre described in In Cold Blood.
It seems quite possible to me that a couple of young psychopaths got together and did this primarily for the thrill, and ended up picking the Rs just because one or both knew the details of their living situation, and didn't like them
Also, in terms of LE keeping quiet,
I think that's increasingly standard operating procedure now. The reason is that
people will confess to crimes they haven't committed, and be really persuasive about it, especially if police are feeling anxious to solve the crime.
Then, in some cases, they turn around and sue police for millions for wrongful persecution.
For example, in the Waddell Buddhist Temple massacre of 9 monks, by two stupid teens, a group of 4 young men who confessed, but were then exonerated, were awarded $2.8 million in an out of court settlement.
http://www.miranda-vs-arizona.com/220FalseConfessionsTheTucsonFour.htm
So I think police services have learned to keep most of it back, to ensure the case
doesn't get bungled by false confessions.