gangster vs gunman

gangster

noun
  • A member of a criminal or street gang. 

  • A member of a professional criminal organization; a racketeer. 

verb
  • To act like a gangster; to commit street crime or run a racket. 

gunman

noun
  • A criminal armed with a gun, especially a professional killer. 

How often have the words gangster and gunman occurred in a corpus of books? (source: Google Ngram Viewer )