BOSTON (NBC) — Retired Boston hitman John "The Executioner" Martorano testified on Tuesday that he and James “Whitey” Bulger were “up to our necks in murder” by the time he committed what he described as his last killing at Bulger’s behest, more than three decades ago.

The former underworld killer also described his one-time boss as having a direct hand in a murder, saying Tuesday that Bulger gunned down a Boston bar owner for bragging about his ties to Bulger's "Winter Hill Gang."

"They took him out in the phone booth," Martorano said of the 1975 murder of Edward Connors, Reuters reported.

"I heard the shots. They came back and said, 'He's gone.'"

Martorano, 72, spent a second day on the witness stand in the famed mobster's racketeering trial. A one-time altar boy who notched 20 murders on his belt working as an enforcer for Bulger, he’s now a star prosecution witness intent on sending his former boss to prison.

Short-spoken and with a prickly sense of honor, Martorano said he was best friends and confidantes with accused Winter Hill Gang leader Bulger and his partner Stephen “The Rifleman” Flemmi.

Martorano has been free since 2007, having served just 12 years in prison after striking a plea deal that centered on his testimony.

Monday, Martorano tied the 83-year-old Bulger to a murder for the first time in the trial, saying that Bulger watched from a car as the hitman rubbed out another victim, Alfred Notarangeli, on his orders in 1974.

In a matter-of-fact monotone, Martorano has told his bloody tales many times – how he disguised himself in a butcher’s coat, construction hard hat, and false beard before shooting one victim at a Medford, Mass., restaurant in 1973, for example.

Or a triple-murder Martorano carried out five years earlier, when two teenagers caught bullets intended for a man who had slighted Flemmi.

Martorano himself committed perhaps his most sensational murder when he gunned down Roger Wheeler, the chairman of Telex Corp., in 1981 at a Tulsa, Okla., golf club. Bulger was at the center of that murder, too, Martorano has said.

Then Martorano says he killed his friend John Callahan to cover up Wheeler’s murder, again at the prompting of Bulger and Flemmi, he said Tuesday, according to the Boston Herald.

“They were my partners, and we were up to our necks in murder already,” Martorano said of what he’s described as his last slaying.

He liked guns to carry out his handiwork, telling CBS in a 2008 interview: “It’s the easiest way, I think.”

“I think I stabbed one guy,” he said.

Whatever his body count, Martorano says he’s not a hitman because he didn’t get paid to end lives. His services came free for friends, he said, out of a sense of loyalty.

“A hitman is a, that sounds to me like somebody’s getting paid, a paid contract. You could never pay me to kill anybody,” Martorano said. “I might be a vigilante but not a serial killer.”

If there’s one trespass the confessed murderer says he will not forgive, it’s the way Bulger double-crossed him. Prosecutors contend Bulger and Flemmi were informants for the FBI.

“After I heard that they were informants, it sort of broke my heart,” Martorano said. “They broke all trust that we had, all loyalties, and I was just beside myself with it.

“I’ll go along with a lot of things, but not no Judas, not no informant. I never informed or ratted on nobody, and if I could have killed him I would have killed him, but I wasn’t there, and that’s what I think he deserves,” Martorano told CBS.

He’ll exact his vengeance on Bulger on the witness stand, he’s said, but that doesn’t make him a snitch.

“One’s got the courage to stand on the stand, the other one’s doing it behind your back and dropping dimes,” Martorano said in the interview. “How can I be ratting on a guy who’s been the rat for 30 years? I’m trying to stop him from ratting anymore.”

Martorano got $20,000 in walking money from the Drug Enforcement Administration when he was released from prison, the Boston Globe reported, and more in royalties from a book about his life.

“In some ways he did get away with murder,” U.S. Attorney Donald Stern told CBS in 2008. “The only thing worse than this deal was not doing this deal. Because if we didn’t do this deal no one would have received any punishment for these murders. Corrupt law enforcement arrangements would not have been uncovered and prosecuted, and the cancer in law enforcement that existed in Boston for a number of years would have remained there.”

Stephen Davis, brother of an alleged Bulger victim, told 7News on Monday after Martorano's testimony, “I’m glad to see them cutting each others’ throats, you know what I mean.

“That’s what kind of guys they were.”

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