Thanks for the research and time that went into this thread. Took me sometime to work my way through it, it is impressive.
I personally believe that the known details point toward a murder suicide. The mental illness, the 11 page 'hate letter', Sherilynn's missing gun (has this still not been found?). This seems like a family annihilation to me. Cases of parents killing children (then often themselves) are less rare than some believe. Considering the hate letter it could have possibly started with Sherilynn shooting Bobby before turning the gun on a possibly hysterical Madyson and then herself. Doubtless this is an awful scenario but seems more likely to me (statistically) than a third party or stranger killing a small child and parents.
Now the main problem with my theory is how they got to the area they were found in. I acknowledge that its unlikely for Bobby and Madyson to be walking this far across such rough terrain. But it is always possible that they did get disorientated and lost, due to this they may have taken a shortcut and found themselves in more trouble. They may have been pushed on by Sherilynn with a gun, as unlikely as this sounds. It is certainly a distance than can be covered by foot though - it is by no means an unassailable distance, especially if for some reason they got a ride with someone part of the way for whatever reason. Perhaps someone gives them a ride (that they meet on the one way road) for some reason (to scout an area?) and tensions become explosive when the family start to return to the van?
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