I feel like Doug changed a bit in episode 3. He seemed more outgoing and defensive.
For example, he shoots a bandit in the face (Sorry, couldn't find one without commentary) http://www.youtube.com/watch?feature=player_detailpage&v=LZu8Im3IUlY&t=116
Then, there's the scene in the RV when Lilly accuses Ben of stealing, and Doug says "But we have our health!" in a tone of voice that seems not Dougish.
Almost...aggressive. It's subtle, but there.
And then... the final scene with Doug. He defends himself and Ben, which is quite odd for such a shy, calm, passive-aggressive man like him to do.
But even though he calmly argues with Lilly, he says "Evidence or not, This isn't a way to treat one of US!" to which Lilly tells him off, and he gives her a dirty, angry look, very similar to this -- :mad: -- . Even though it's just for a few seconds before the camera cuts to Kenny, it's very odd for him to dirty look someone like that. (http://www.youtube.com/watch?feature=player_detailpage&v=LZu8Im3IUlY&t=527)
So, in short, I feel like what lee said was true. "Shooting people changes you"
I feel like Doug was become more outgoing and tough almost, being brave enough to jump in front of a bullet for his friend.
It's a shame he died shortly afterward, I would have liked to see how the story would've played out had he survived and became more outgoing and tough, maybe even stand up for himself and shock all the players, like Ben in episode 5.