So, first day on here, the web and this form, and, already, I have a theory. Kevin and Don's murders are related to Billy and Dennis.
Both Billy Don Hainline and Dennis Ducker were killed on a railroad, roughly 310 miles away, 3 years apart. Billy and Dennis were found with small amounts of alcohol. They both have the feeling of foul play, and, everything in here, is going to be a stretch.
To put it simple, they were killed by the same people, person, whatever. It's a possibility that they were both involved with a cartel or trade or something, thus explaining why it was on the train tracks. Maybe they were nosing around into something they shouldn't have been.
And then the cover up, maybe the police were bought out, threatened, something. And with the fact that Billy Jack Haynes said that it was most defiantly a government or federal involvement.
To me, this just screams that they knew something they shouldn't have. I really couldn't find to much, but, this is the best I can do for right now.