Colorado isn’t the same as it was when I was growing up there. Back then (70s - early 80s) a dude like this would simply disappear. Cops would have “no clue” as to where he got off too. Some years down the line an Elk hunter or hiker might come across some bones and he’d be identified, but no one would have a clue as to how he got there.
Today, the main job of the police is to protect Bad Guys from the Good Guys so that what you describe does not happen. Bad Guys are mostly protected by the system, and law-abiding Good Guys live in some degree of fear because they are not allowed to take out the trash. The rulers like it this way.