Billy didn't want much in this world except for his mother to be happy and his brother to straighten up and quit getting into trouble.
Now they are dead and Billy is charged with their murders.
A long lost uncle bails Billy out and makes him jump bail to work with his old associate in California.
Within a week of being in California's criminal underworld he is picked up by an FBI special agent, who uses Billy as an off the book informant.
This is how Billy becomes a hitman
This is how Billy becomes a rat
This is how Billy gets revenge