Bertolt Brecht said this quote

The first time it was reported that our friends were being butchered there was a cry of horror. Then a hundred were butchered. But when a thousand were butchered and there was no end to the butchery, a blanket of silence spread. When evil-doing comes like falling rain, nobody calls out stop!When crimes begin to pile up they become invisible. When sufferings become unendurable the cries are no longer heard. The cries, too, fall like rain in summer.