Maybe I'm missing something but in the beginning of the book Danny takes out all three killers shortly after his mother and sisters are killed. Just beyond chapter 24 it says Danny waited a year before killing his mother's killer. Did I miss something?
I had to re-read that too. He initially killed the 3 that came back to the house for the pack. It is not clear how many soldiers were in the house to begin with, but I assumed that the man who actually killed his mother had not returned to the house at that time.