'Whitey' Bulger and Former Pal Trade Curses in Courtroom

July 9, 2013— -- A Boston federal courtroom sounded more like a South Boston street corner today as foul-mouthed threats were exchanged between alleged gangster James "Whitey" Bulger and his former right-hand man Kevin Weeks as they accused each other of being "rats."

Weeks was nearing the end of his second day on the stand recalling drug deals, extortions and murders he said that he had committed alongside Bulger.

During cross examination by defense attorney J.W. Carney, Weeks was asked if he had any remorse about the people he confessed to killing. Weeks, who Bulger had once described as a "surrogate son," answered that he did feel bad.

"Because we killed people that were rats and I had the biggest rats right next to me,'' Weeks testified, looking at Bulger, who records show was an informant for the FBI, but which he debies.

That prompted Bulger to mumble, "You suck."

Weeks, 57, then yelled, "F*** you, okay."

Bulger, 83, shouted back, "F*** you too."

Weeks made a motion to move from the witness stand while asking, "What do you want to do?"

At that point federal Judge Denise J. Casper interrupted the outburst.

"Hey. Mr. Bulger. Mr. Bulger. Let your attorneys speak for you,'' she admonished the reputed gangster who is on trial in connection with 19 murders and other crimes allegedly committed as the boss of the Winter Hill Gang.

She then turned to the witness and added: "Mr. Weeks, here's how this works: You answer the questions, okay?"

Carney was also taunted by Weeks, after asking him what he would do if someone called him a rat. The witness responded, "Let's step outside" and find out.

"It was pure chaos in the court. It jolted everyone,'' said Steve Davis, the brother of a woman Bulger is accused of killing who has been in the courtroom every day. Davis had already been jolted after hearing evidence about how Weeks, Bulger and Stephen "The Rifleman" Flemmi allegedly murdered his sister Debra.

Weeks testified about the murder Debra Davis in grisly detailed. He said Bulger told him that Flemmi – who had dated Davis since she was a teenager – wrapped duct-tape around her mouth; kissed her on the forehead; and whispered: "You are going to a better place."

Davis was then strangled and her teeth and hands were removed. Weeks said he didn't know which one of the two gangsters strangled Davis, one of two women Bulger is accused of killing.

Weeks led investigators to her body when he decided to cooperate with investigators.

"Carney was asking Weeks if he ever lied and Weeks said of course I lied. I'm a criminal. But now it's like he wants us to believe that today he is telling the truth about his lies? I don't know what to believe," Steve Davis told ABC News. "I just pray the day comes when they get what's coming to them."

Davis is slated to take the stand next week, he told ABC News. "It was a wild day in the courtroom. I hope the jurors took note that everyone in this case is rotten to the core, opportunistic liars," he said.