Nick Calabrese, Chicago Mob Hitman who Turned Government Witness has Died #FamilySecrets

Nick Calabrese

Former Chicago mob hitman Nicholas Calabrese has died, a source said Monday.

A source confirmed to CBS 2's John Drummond that Calabrese had died. Calabrese was 80.

Calabrese was infamous as a top assassin for the Mafia in Chicago. Among the 14 murders in which Calabrese told federal prosecutors he took part were those of brothers Tony "the Ant" and Mike Spilotro. Tony Spilotro was the Chicago mob's man in Las Vegas and the inspiration for Joe Pesci's character in the 1995 movie "Casino."

Calabrese later became known for turning on his brother, Frank Calabrese Sr., in the Operation Family Secrets probe that took down several prominent organized crime figures.

Frank Calabrese Sr. was known as a brutal loan shark. During the Operation Family Secrets mob trial in 2008, he was charged with 13 murders.

During that trial, Nick Calabrese gave graphic details about how his brother strangled his victims and then slit their throats.

Frank Calabrese Sr. was convicted of seven murders and, two years later, was sentenced to life in prison. Frank Calabrese Sr. died in prison in 2012.

In addition to Frank Calabrese Sr., fellow Outfit figures James Marcello, Joseph "The Clown" Lombardo, Paul "The Indian" Schiro, and Anthony "Twan" Doyle were the main defendants at the trial, and were convicted on conspiracy and racketeering charges. A jury also found Frank Calabrese Sr., Marcello, and Lombardo responsible for 18 murders in all.

Meanwhile, Nick Calabrese was sentenced to 12 years and four months in prison in 2009 for the 14 murders to which he admitted.

Nick Calabrese was most recently said to be in the federal witness protection program.

Thanks to CBS Chicago.