Sammy Gravano

Salvatore "Sammy the Bull" Gravano is an American former mobster who rose to the position of underboss in the Gambino crime family. As the underboss, Gravano played a major role in prosecuting 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.