One of my earliest memories of going to the library was when I was about 3 and a half. My mother and I were once reading a book about a baby hippo. It was a small book with simple illustrations. All I remember is that these men came and took away the baby hippo's mother. I think (and my mother thinks) she stopped reading soon after so as not to continue reading an apparently disturbing book with me.

Is anyone familiar with what book this was?