That's funny...I didn't really like the film until the ending. It was shocking and not at all what I was expecting, and I tend to like that sort of thing.
Why did there need to be hope for this thing to have worked. Granted, the shooting did not fit well with all of the other ambitious plans the characters acted on during the film, but most everyone died as a result of those plans, didnt they? At the end, this guy has death all over his hands and, unfortunately, was also looked to as the voice of reason. These events did not unfold over the course of 2 hours for them as they did for us, and by the time we come to the end, they are defeated and out of options. Sit, wait, starve. Hope? Maybe, but what kind of fantasy world do you live in where the absence of hope makes for an unrealistic ending.