I`m starting to think that the train is this person`s will, as it is the only thing that moves and that lights out the world. I also think that this train is this person`s need for change and hope, since all the background is empty and and silent, altough it is a city. It might be that he want`s to start a new life, far from his home and far from his family, that, given by the fact that the sun is at sunset, and he`s moving away from it. In fact, i think it`s even more than that, i think that this person is not a gunman yet, but he wants to be, and this is his first step as one, this is the moment from which on he becomes one, from now on, this is his life, this is him. A secondary opinion is that his family and past are dead, so, his sun, being his happiness, goes away from him to a place he can`t reach no matter what, then, the train represents his only salvation, his motivation and will is the only thing that can save him from emptiness and from being lost.