It was designed to select people by way of genetic markers, as opposed to personality traits, status, or even my personal feelings on them. It wasn't designed to kill everyone, and when I realized it would do that, I revised it until it wouldn't. The people that died would die instantly instead of suffering; the people that survived would be something that I considered superior to humanity in the end.

It doesn't change how terrible the attempt was, or how hideous the outcome would have been. But if I had to end the world, there were far crueler ways that it could have been done, and I went out of my way to avoid them.