Maurice didn't deserve that bullet in my opinion. Aiden is a selfish dick, like you say, but at that moment he has the choice to not be a selfish dick. He did (in my game) what he should have done from the start, walk away.
My brother recommended it to me, also. I have it downloaded and I'll play it tonight. He told me that after playing it he was absolutely terrified, just frozen with fear. I'm looking forward to playing it!
Update: I found two pages, then saw him in the distance. I, I don't want to talk about it anymore...that sound...
Seriously, if you are interested in horror games: Play this.