Official Sammy The Bull Salvatore "Sammy the Bull" Gravano (born March 12, 1945) is an American gangster who became underboss of the Gambino crime family. Gravano played a major role in helping the prosecution sentence John Gotti, the crime family''s boss, by agreeing to testify as a government witness against him and other mobsters in a deal in which he confessed to involvement in 19 murders.