It is very unusual for one person to be left alive.
Appypappy, you say you knew one of their nephews, so I don't want to be offensive; after all, I don't know the family. But, jaded as I am from terrible news stories, I did wonder why one of them was left alive...I've heard of this before, and I know what the outcome often is.
Did you think the same thing? I could very well be completely off base, but the suspicion did enter my head.