People said the four adults agree to suicide themselves, but I see it different, I think David shooted them without too much doubt, thats why you can feel his pain at the end, he just murder them as a way to save them..ironic...but a more effective situation...
shareHe shot them all, and it wasn't suicide. The shots were too rapid for individual suicide. (Especially his son wasn't going to shoot himself without a lot of questions beforehand!) Hence his reaction after he saw help was on the way after committing his merciful act.
shareI've never even heard of the suicide ending. I thought it was a given that he shot them. It wouldn't make any sense at all, not sure why anyone would think that.
shareIt's obvious that the old guy, and presumably the old and young women agreed to be shot by David.
His son was also shot by him, better dead than mutilated by terrible creatures.
He was one bullet short. I thought they showed that.
He mercy killed all the others then intended to go out and meet his fate, but the mist cleared up. That's why he was in anguish: he sacrificed all the others, including his son, for nothing.