Innocent girl home situations

Life is so dengerous for people. Innocent people are killed and they kill them with bite. The anonymus come and kill and hide their own face...
Why???
I don't know why? Why they do like this? Why they kill innocent people? Why are they in the earth? Why? Do they love?

I think... yes... they love because they also have obsession to get their love. But probably they also suck their lover blood.