Prolific Chicago mob hitman Frank Calabrese Sr. has died, authorities said Wednesday.

The corpse of Calabrese Sr., who was in his mid-70s, was expected to be delivered later Wednesday to the chief medical examiner's office at the University of North Carolina from the Butner Federal Medical Center, the office's autopsy manager said.

No cause of death has been determined, but Calabrese suffered from several ailments, including heart disease, the Sun-Times is reporting.

A federal jury and judge found Calabrese Sr. responsible for 13 murders in September 2007 as part of the historic Family Secrets mob case. Calabrese Sr. was sentenced to life in prison.

His son, Frank Calabrese Jr. ­— who risked his life and secretly recorded his father in prison as he bragged about mob murders — said Wednesday he had "a lot of emotions" running through him.

"It's very emotional right now because there were two sides to my dad, and I miss the good side," said Calabrese Jr., a key witness against his father at trial.

"I believe he was taken on Christmas Day for a reason," Calabrese Jr. said. "I hope he made peace. I hope he's up above looking down on us."

"It's always been hard for me that he had to be locked up like that. Then again, I didn't forget a lot of the things that happened," Calabrese Jr. said. Calabrese Sr. was known for not only the terror he inflicted on the streets, but also the violence he visited upon his own family.

"He's not suffering any more. The people on the street aren't suffering any more," Calabrese Jr. said.

-- Sun-Times

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