I am completely surprised not one person mentioned this or how it is not mentioned in the wikia, but Chuck is a lot bigger of a character than it seems.
Play episode 3 again, and when you first enter the driver's room and see the dead body, remember how the guy was not killed by the walkers, nor turned into one, but was MURDERED? He didn't kill himself, someone shot him from the outside as evidenced by the glass. Now in this room, did anyone look at the photograph? It was a man with his wife and two kids. Guess who that was. Yes, Chuck.
Why would his picture be attached in the driver's room? Remember how Chuck just so happened to be living at the train? How the train somehow stopped on its own and was shut off? Remember how he strangely happened to be in the sewer with a gun that was never seen before, and how Vernon questioned Lee about the train? Is it weird that both Chuck and Vernon look alike? Lastly, did you notice how the picture disappeared after talking to Chuck for the first time and heading to the driver's room to find it missing? This cannot be a coincidence. Chuck used to work as a train driver, and Vernon knew about it.
So, what am I trying to get exactly? Well here is what I think. Chuck lied to Lee about not seeing his family in fourteen years. For all we know, he was probably on the train the day of the outbreak and after seeing what happened and the train stopping to possibly avoid hitting a car (seen next to the train where that zombie was inside still attached to the seat belt.) Chuck, who knew what was going on and was too afraid to take chances, shot the driver and shut off the train, using it as shelter. Possibly fearing death, he chose to stay indoors, going out only to find food and whatnot, drinking to keep him calm, assuming his family are dead.
Seeing how Kenny had the same drinking habits, this is very likely. Now here is where Vernon's story comes to mind:
Vernon and Chuck knew of their occupations and area of residence. When Chuck chose to fight off the walkers himself, he looked very confident. It appears that he still had his gun all along and used it to defend himself from the horde of zombies. Then, he went to go meet his brother and the cancer group on his own and possibly get them to help Lee. Realizing he was outnumbered and could not make it in time, he took his life with the last bullet of his gun.
Vernon, knowing of Chuck's occupation, went to the train, possibly to see if he was still there and also to see if they can use that as a method of transportation. As we don't know what happened to the group, this is probably the case.
Anyone want to say why you agree/disagree? Feel free to discuss.