Frank Calabrese Sr. passed away last Christmas and his son remembers his father, revealing family secrets and moments he spent with his father.

The first incident Frank Calabrese Jr. talks about his when his father came home one night when Calabrese Jr. was a teenager and took him into the bathroom for a chat.

"He used to like to talk in the bathroom with the fan going and the water running in case there was any kind of bugs in the house," says Frank Jr in an interview published in npr.org. "I could just see his adrenaline going. And he was telling me that they killed somebody, and the reason they did it was because the guy was dealing drugs and he was disobeying his boss. He's telling me this and I'm thinking, 'Is this what other kids hear when they come home and their father comes home from work?' "

Frank Calabrese Jr. admits that he always knew his father was no ordinary father, what with being  one of the central figures in the Chicago mafia, responsible for a series of loansharking and illegal gambling operations.

In 1997, Frank Sr. was sent to prison along with his brother Nick and Frank Jr. on a series of racketeering charges. The feds had enough evidence to keep him in jail for 118 months - meaning

Frank Sr. was arrested in 1997 but with the evidence the police had, it was enough to imprison him for only 9 years and 10 months after which he would have been a free man. However Frank Jr. decided to help out the FBI and bring the Chicago mafia down.

"[I wrote that] I didn't want immunity. I didn't want any kind of deal. I didn't want to lose any time, but I want[ed] to help [the government] keep my father locked up."

According to Frank Jr., his father was too dangerous to walk out a free man. So, on a visit to his father in jail, Frank Jr. wired up so that he could get evidence of his father talking about all the crimes they had committed.

"I didn't push anything," he says. "And my father [had] taught me two ways to get a guy to talk: Either feed him a lot of liquor or get him mad. So we didn't have any liquor in jail, so I got my father mad. And the premise was that we were working on our relationship. So all this stuff he was talking about really wasn't forced."

From the recorded conversation, the FBI were able to collect evidence of Frank Sr. admitting to committing several murders "in great detail."

"I knew the day I wrote the letter that my life was going to change, and I knew that the day I did the letter that I would be sitting on the stand in the same room as my dad," he says. "What I never thought about was the emotion that would come over me as I walked in the courtroom after not seeing my dad. ... I wanted to run over and hug him. ... But after five minutes of being on the stand, it didn't take me long to have that love for my dad turn into hatred for my dad and remind me of what I [was] doing."