God(s) did the same thing in Noah's story. Only Noah and his family and pairs of animals were allowed to live. the reason for the flood was because the change of heart in humans. humans became dirty with greed, envy, and such as well as the blood of battle (killing someone overall in that sense). its sad but its how they purify things.
Death is the only way to purify things?
Its so complicated to think and talk about it right :)
But I like stories that think about it even if they use metaphors
lol you'll see it in many stories. even stories where fire is used to burn a whole town or village to purify it of diease and such exist.
but is was a belief back then and is still believed to this day in some countries. if it meant peace and rest, then the act was done. even movies protray about it. the movie The crazies is a good example of it. look it up if you've never watched it.
http://www.imdb.com/title/tt0455407/
Maybe it's seen as if something is "impure beyond salvation" the only way to get rid of that impurity is to get rid of the thing itself, the medium to reach that can change, but in all cases it means death to the living and inexistence for everything else ┑(°へ°)┍
So the God turned to Sheetsu cause of the change of humans' heart... Thats sad thoΣ( ￣□￣||)