Hand of Vengeance by Marc Alexander

He's a young boy but his mother is drilling names in his head and making him swear he will avenge his father's death.  When he grows into a young man, he heads out to take his revenge on the men who shot him down in their yard...

Pioneering Press sent me a copy of this book to read for review (thank you).  It has been published and you can grab a copy now.

Saul has a mentor.  The professor gets a gunman in to train him in how to be a fast and quick shot.  Then he searches down the victims.  Saul is thankful for his help.  It isn't until later that he finds the professor is making money by writing articles about his exploits.

He fights them fair and wins his fights but he's getting tired of killing before he's done.  He's also having trouble with women.  One of them shoots him in the arm so he can't kill again.  He exercises his arm to get motion again but she didn't really slow him down.  He can shoot just as well with his left hand.

When he gets to the last man, he learns the truth about his father.  He decides not to kill him.  This enrages the professor.  It also almost gets Saul killed.  

The ending is very ironic.  I liked it a lot.