So why write in this novel that he was shot in the arm? 
I think he was hit in the shoulder. And the shoulder and chest are not that far apart.
And one other thing that troubled me was that no mention was made of Sonny seeing Vito kill Fannucci. In this novel he says that he saw Vito kill Tom's biological father, but never references his witnessing Vito killing Fannucci.
In this novel Falco based Sonny's ago on the movie timeline. I always thought it to be a little strange that a three or four year old Sonny would be able to go outside alone and follow his father over the roof, and last but not least, that he would even remember seeing such a thing at that age. That's why I think in this novel Falco changed it to Sonny seeing Vito murdering Tom's father when he was younger.
