The Rape of Nanking: The Forgotten Holocaust of World War II

I know little about WWII since I used to quite ignorant to history class when I was in school. A few information that still stored in my brain, i.e: Nazi holocaust, Nagasaki & Hirsohima, Pearl Harbour, and of course Dutch and Japan colonization over my country, Indonesia. But that's all. I never heard about Nanking massacre which is very devastating I just can't imagine how people can be so evil I hope that's not real and only see them in movie :((