This is something you say when you really are shocked by something! The impression is so big that you only can say it like that! You see a tsunami or a tornado! Or a planecrash! Maybe a boat sinking! Or war! These words are somehow connected to disasters. I don’t know why. It’s also the tone in your voice when you say it that connects it? I think. Anyway I will say something more positiv next time i write something!