Complex sentence: Twenty years later, Goodkat and Slevin killed The Boss'son and both mobsters' bookies, stealing the bookies' ledgers in the process; after finding Nick Fisher owed a great deal of money to both sides, they killed him and stole his identity.
Split into simpler sentences: Twenty years later, Goodkat and Slevin killed The Boss'son and both mobsters' bookies, stealing the bookies' ledgers in the process. After finding Nick Fisher owed a great deal of money to both sides, they killed him and stole his identity.