Shane was a nice guy that made some bad choices which pretty much led to whatever happened. Not that he deserved anything, not at all, but he was living a risky lifestyle so to speak. I think the police and most of the public are confident that the last person that he was seen with knows what happened and where he is, but there is no physical evidence and he's not talking. There was a disagreement before that day that had not been resolved. That person is currently doing time for gun store robberies that occurred after Shane disappeared. There is also speculation that maybe one or two others may be involved but so far nothing concrete has come up on that either.
It would be good if he can be found so that there is some kind of closure but at this point there may not be enough physical evidence left to point to anybody. The police have made it clear that they don't think that he's alive and we don't either. Hopefully somebody will slip up and say something that leads to this being solved. If there was only one person involved and he hasn't said anything at all by now though some of us are afraid that may never happen.
Welcome to WS, JYN_Reptilez.
I think it's extremely important that the "No DNA Sample Available" be accurate on NamUs and is not an oversight. If you're part of or in touch with Shane's family, perhaps you can confirm that it is indeed correct.