I just thought of something. Speculating.
Seems like regardless of the "reasons" given, there was to be a specific gathering of the Rhoden men on Friday.
DS came in to "work on cars" Gary arrived for same reason?
Even young Chris was there. Was he supposed to be there that night?
Where did Chris usually live?
(Do we have any solid info. on exactly where (location) each Rhoden lived on 'normal' days?)
With women and children also there, the Rhoden men did not expect trouble.
Maybe the "unknown persons" scheduled a meeting on Friday for what seemed to be harmless reasons.
Rhoden men gathered at Rhoden homes. DS was expected to be at Kenneth's, but wasn't. Coincidence?
Early morning when all are asleep, the Rhodens were ambushed.
IF this theory has merit, possibly phone records give LE a lead.