Stephen “The Rifleman” Flemmi testified today he was a man torn apart by the intense jealousy of his partner James “Whitey” Bulger and his needy young lover Debra Davis — a tug-of-war he said Bulger won by throttling Davis in 1981.

“It affected me. It’s going to affect me until the day I die,” Flemmi said of his reluctant decision to help kill the bombshell in a house his mother had just purchased in South Boston next door to Bulger’s brother, former state Senate President William “Billy” Bulger.

“I loved her,” Flemmi said dispassionately of Davis, “but I wasn’t in love with her.”

Davis’ brother Steve Davis later fled the packed courtroom, his face scarlet red and his jaw clenched.

At least one juror broke down in tears, no doubt recalling the stomach-turning photographic images from state police of Davis’ skeleton wrapped in rope and her skull, still matted with blond hair, in a plastic bag, as she was found in her crude grave.

The second day of the 79-year-old Flemmi’s testimony against the accused 83-year-old mass murderer with whom he claimed he took multiple lives right under the noses of the FBI they served as secret top-echelon informants was not punctuated by any of the profanity laced fireworks that went off yesterday during their first 10 minutes together.

In fact, the two men completely ignored one another for the nearly four hours Flemmi was on the witness stand in U.S. District Court.

Still, it’s been established that during their 18 years apart, while Bulger was on the lam living seaside in Santa Monica, Calif., and Flemmi was being sentenced to life plus 30 years, absence did not make their hearts grow fonder.

Davis was 26 when she died. Flemmi, then married, met her working in a jewelry store in 1976. Four years later they were sharing homes on Longwood Avenue and in Randolph.

“He (Bulger) wasn’t too happy about my relationship with her because it started interfering with our business,” Flemmi said of his equal in the Winter Hill Gang hierarchy.

“She needed quite a lot of attention,” he said. “She was a young girl.”

When he wasn’t fighting with Bulger about the nights he was spending with Davis, Flemmi said he was fighting with Davis about the days he was spending with Bulger.

Flemmi signed Davis’ death warrant when during one of their snits at a birthday party Bulger was trying to call him and he “blurted out” that he and Bulger were in bed with an FBI agent named John Connolly.

“He wasn’t too happy about that,” Flemmi said of Bulger’s reaction.

Assistant U.S. Attorney Fred Wyshak Jr. asked Flemmi how Connolly took being outed.

“He wasn’t too happy about it, either,” Flemmi said.

Further irking Bulger was the amount of money Flemmi was throwing at Davis to keep her happy.

“I bought her a Mercedes,” he said. “I sent her on vacations. I gave her money. She had a lot of jewelry. People started noticing that.”

Bulger feared people noticing Davis would lead to prying eyes noticing them, as well. Davis had to die, he told Flemmi.

“I said, ‘No, of course not. Why?’ He said John Connolly had protected us and now we’re jeopardizing all that.”

Eventually, he said Bulger wore him down and he delivered Davis to him in the empty house his mother was preparing to move into.

Flemmi admitted he was weak and could not bring himself to do the deed.

“Bulger said, ‘I’ll take care of it,’” Flemmi said, and when Davis walked in he said Bulger grabbed her by the throat and strangled her as he was dragging her down a flight of stairs to the basement.

Wyshak asked Flemmi what he was doing the whole time his girlfriend was fighting for her life.

“Nothing,” Flemmi replied. “That was the plan.”

Once Davis was dead, Flemmi said Bulger took a nap on a rug on the floor because the furniture hadn’t been delivered, while he stripped Davis naked to help hide her identification if her body was found.

He said he wrapped her in a tarp and bound it with rope. They then buried her remains in a marsh beneath the Neponset River Bridge.

Flemmi dug the hole while Bulger sat and watched, he testified.

“Why didn’t he help?” Wyshak asked. “Did he just let others do the dirty work?”

Flemmi appeared momentarily perplexed.

“That’s what he did,” he said, shrugging.

Davis’ remains were not located until late 2000.

Flemmi returns to the witness stand Monday for continuing direct examination by Wyshak.

Members of the public started lining up outside U.S. District Court at 1:45 this morning for one of 320 seats available to them either in the trial courtroom or four other overflow rooms where they can watch on closed-circuit television.

Flemmi pleaded guilty in 2003 to his role in 10 murders — a deal that enabled him to escape the electric chair in either Florida or Oklahoma for the executions of John Callahan and Roger Wheeler.

Bulger, who he was with from 1974 to just before Christmas 1994, is defending against 19 murder charges, including Davis.