Frank Calabrese Sr., Hit Man for the Chicago Mob, Dead at Age 75

Frank Calabrese, a former hit man for the Chicago mob, has died in prison at the age of 75. Officials have not released a cause of death, but the news has brought closure to many of the families who lost loved ones to Calabrese and the mob.

"It's very emotional right now because there were two sides to my dad, and I miss the good side," his son, Frank Calabrese Jr. told the Chicago Sun-Times.

The two shared a complicated relationship, as Calabrese Jr. helped put his father behind bars by wearing a wire and recording him talking about his killings for the mob.

Calabrese Sr. was notorious in the 1970s for mob-ordered murders that involved a great deal of violence and bloodshed. According to Calabrese's brother, he "preferred to strangle victims with a rope and then slash their throats to make sure they were dead," according to the Associated Press.

During the trial, which took place in 2007, his family turned on him and revealed family secrets such as the fact that Kurt, Calabrese's son, felt that his "father was never a father – he acted as an enforcer to me" and threatened to "bite your nose off" and make him "disappear."

Calabrese Sr. died on Christmas Day, which was an especially emotional time for the family, his lawyer, Joseph Lopez told the Chicago Tribune. "It was his favorite holiday of the year," and "he always talked about how much he loved spending Christmas with his family."

Calabrese Jr. also maintained that his father often "manipulated religion" to get what he wanted. "He used religion as a way to get people to open up and trust him. The way he understood religion is different than the way religion is supposed to be understood."

"His passing on Christmas is his way of telling me he's made peace with God," Calabrese Jr. told the Tribune. "He's with God; he's with heaven. He's over my shoulder making sure I don't make those mistakes again or go back to the person I was … or he was."