IMO there is nothing wrong with his gait. He's probably in his 50's and he's lumbering along like we men in our fifties tend to do. We are not youngsters anymore you know.
About his hands in his pockets. For some reason, I simply feel that this guy likes to put his hands in his pockets, when he's walking, standing, or whatever. He's one of those guys who always has his hands in his jacket pockets. Some people like to stand and walk like that.
IMO it is not possible that he was drunk. He's way too good for that. I do not like all these drifter theories because too me this guy is quite skilled at these nasty things he does. He's very good at it.
For some reason, they are looking for anyone who might have seen someone throw down a backpack beside a highway. There is also mention of a duffel bag. I have not the slightest idea what that all could be about. I doubt if he hitchhiked away though. That's too stupid. He's way too good for that.