It isn't an improbably scenario that Lucas and Chynna were followed for some time, perhaps a few days.. I watched that vid clip of them at the service station, so casual about showing affection so naturally, and how that would , under the wrong circumstances , at the wrong time, infuriate someone who's grip on reality was frail.
Perhaps someone who wanted to let go of the grip on reality, a terrible temptation to a killer flirting with the idea. Perhaps their planned route was overheard.. all theory but not improbable, and not for the first time, either. .
He was working at the ranch since Feb. She arrived on July 6. They spent a week together at the ranch.
They started their trip on Saturday, July 13, so the 7:30PM video is from the day they left the ranch. July 14 at 3:20PM they were stalled. July 15 at 7:19AM they were deceased.
They were only 4.5 hours from the ranch when they were murdered.
The other point is that they were headed North, and the suspect was headed South when seen by the witness on Sunday evening. It is still possible that they were followed from the gas station, but then why didn't something happen on Saturday evening? It's also possible that someone passed them heading North, turned around, and accosted them while facing South.