Detective Ray's summation is entirely possible, that person could've gotten into LE or the legal system with his sense of justice to play out. However, If this is the case I don't think he worked alone, a friend, or relative who believes the same, or more people in a small group. If this is the case he's possibly traveled outside his area, to execute two other families, or maybe killed more in different places other than their homes. Wouldn't it be easier for them, in their minds, after the first one, for their warped sense of vigilantes being fed?
It would be interesting to see if any unsolved murders in surrounding counties have evidence to show the same person doing these crimes. I know alot of area Sheriffs got together with Pike County to discuss things when the Rhodens were killed. I would hope they've gotten together for other unsolved deaths in their areas.
vig·i·lan·te-
a member of a self-appointed group of citizens who undertake law enforcement in their community without legal authority, typically because the legal agencies are thought to be inadequate.