The result of Calabrese Jr.'s information was a famous federal prosecution called "Family Secrets."
In the past 12 1/2 years, Calabrese Jr. has moved from mob enforcer, to FBI informant, to government witness, to pizza maker, to book author. And now he has done his first television interview since helping to put away his father and other top mob Chicago bosses.
"I'm either gonna testify against my father and put him away for life or I'm gonna wait 'til we get on the street and something is gonna happen with one of us," said Calabrese. "One of us is gonna wind up dead one of us is gonna wind up in jail."
Frank Calabrese Jr. told ABC Nightline that he chose to put his father away. Junior's book is due out next week: Operation Family Secrets: How a Mobster's Son and the FBI Brought Down Chicago's Murderous Crime Family.
The story that began in 1998, as Calabrese Jr. was doing federal time for loan sharking and extortion with his mob boss/father, Frank "the Breeze" Calabrese.
"For eight months every time I turned around he was deceiving me," Junior said. "He was lying to me, and I decided to write that letter."
The letter to the FBI in Chicago offered to snitch on his dad and the Outfit. "I am sending you this letter in total confidentiality. This is no game," Junior wrote to FBI agent Tom Bourgeois.
Bourgeois told the I-Team that with that letter the FBI opened the Family Secrets investigation.
"My mind was made up that I had to assist with them to keep him locked up," said Calabrese Jr.
Soon his hitman/uncle, Nick Calabrese, turned over Frank Sr. as well, their tandem testimony largely responsible for solving 18 Outfit murders and the imprisonment of 11 top mob bosses.
Nightline shot in a Phoenix pizza restaurant where Calabrese once worked. ABC's Bill Weir talked to him, and Calabrese looks like he ate up the attention.
"When you make decisions like that you can't make them in the spur of the moment, you can't make them 'cause you're mad at the moment or something happens," Calabrese said. "You have to sit down and you have to really think through it. That is not an easy decision to make."
The FBI cooperated with Calabrese Jr. in the production of his book, but a spokesman says that agents did not profit from the publication. Calabrese's FBI handler was also interviewed by Nightline.
The exclusive interview with Chicago's most notorious mobster-turned-author will be featured Friday on nightline after ABC 7 News at 10 p.m. The Calabrese is story so compelling that Nightline's producers have extended the story to two full segments.