WINTER HILL TRIGGERMAN JOHN MARTORANO SPEAKS FRANKLY IN HIS FIRST INTERVIEW -- "60 MINUTES" SUNDAY

The Killer of 20 Says FBI Agent John Connolly Knew that John Callahan Would be Murdered and He Defends His Government Witness Deal

Infamous Winter Hill triggerman John Martorano tells Steve Kroft that former Boston FBI Agent John Connolly knew John Callahan would be murdered - a crime Connolly denies but will stand trial for in a few months. Martorano says he killed Callahan, his 20th victim, because, according to gang boss James "Whitey" Bulger, Connolly said Callahan was going to inform on Bulger and others for another murder Martorano committed for the gang. Martorano's interview, his first ever, will be broadcast on 60 MINUTES Sunday, Jan. 6 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

"Sure [Connolly knew I was going to kill Callahan]. [Connolly] said it, 'We're all going to go to jail for the rest of our lives if this guy doesn't get killed,'" says Martorano. "This is an FBI agent telling it to Whitey telling it to me."

And Martorano will be telling it to a jury when he testifies against Connolly as part of the deal he made to get out of prison after just 12 years -- a little more than seven months each for his 20 victims. But unlike Bulger, who informed on Martorano and many others for decades before becoming a fugitive, Martorano says he is no rat. "I never informed or ratted on nobody," he tells Kroft. "If I could have killed [Bulger] I would have killed him, but he wasn't there." Tipped off by Connolly to his imminent arrest, Bulger went underground 12 years ago and remains a rat in hiding, according to Martorano, who explains to Kroft the difference between him and Bulger. "One's got the courage to stand on the stand, the other ones are doing it behind your back....How can I be ratting on a guy who's the rat for 30 years?"

The day Martorano learned that Bulger and gang member Steve Flemmi had been giving information to the FBI and not just getting it, he says was the "worst day in my life."

The 67-year-old former altar boy portrays himself as a stand-up guy who killed for his family and his friends, to whom he was absolutely loyal. "I mean, you could never pay me to kill anybody....I never enjoyed it. I don't enjoy risking my life, but if the cause was right I would," he tells Kroft. "I always felt like I was doing the right thing. Even if it was wrong, I always tried to do the right thing," says Martorano.

Martorano coolly describes some of the murders he committed and when Kroft points out his seeming lack of emotion, he says he has his regrets and wishes he had committed no murders. But, he says "You can't change the past. I am trying to do the best I can with the future and explain it as best I can," he says. "I regret it all, but I can't change it."