Frank Calabrese Sr., a name that should be familiar to anybody who has lived in Chicago, died on Christmas day at the Butner Federal Medical Center. The mob hitman was 75.

Calabrese Sr. was a well-known hitman for the mob in Chicago who was responsible for numerous murders throughout the city. He was also responsible for a number of loansharking and illegal gambling rings throughout the years.

The noted mobster got his start in the 1950s by providing loans on behalf of the mob to people in Chinatown. He was arrested, along with his sons, in 1995 for using threats, violence and intimidation to enforce a loansharking racket. He was sentenced to 118 months in prison in 1997.

While serving his time in prison, Calabrese was charged in 2005 with murder, racketeering, extortion and illegal gambling as part of the Family Secrets investigation. His son, Frank Calabrese Jr., wore a wire while in prison that gave the FBI concrete proof that Calabrese Sr. was responsible for a number of murders over the years.

Calabrese Sr. was convicted for 13 murders and was sentenced to life in prison. He was currently staying at the Butner Federal Medical Center in North Carolina when he died on December 25, 2012. His cause of death is currently unknown, but Fox News speculates it could have been a heart problem since he reportedly suffered from an enlarged heart.