BOSTON (AP) — A feared gangster known as "The Rifleman" detailed for a jury Friday a grisly string of nine killings he says reputed Boston crime boss James "Whitey" Bulger ordered, approved or carried out with his own hands, including the strangling of the witness' own girlfriend.

Stephen Flemmi said he set his girlfriend's killing in motion when he blurted out to her something he shouldn't have: that he and Bulger were FBI informants.

Bulger decided Debra Davis knew too much and strangled her in front of Flemmi, the once-loyal Bulger associate told a rapt jury at Bulger's racketeering trial in federal court.

"What did you do?" prosecutor Fred Wyshak asked.

"Nothing," Flemmi replied.

"Why not?" Wyshak asked.

"That was the plan," Flemmi said.

Flemmi did show a flash of remorse for killing Davis, who was 26. "It's affected me and it's going to affect me until the day I die," he said.

In rapid succession, the mob turncoat described Bulger's alleged role in eight other killings during the 1970s and `80s when the two men were leaders of the Winter Hill Gang, Boston's Irish mob.

On Thursday, when Flemmi began his testimony, he and Bulger snarled obscenities at each other in a staredown in court. But on Friday, Bulger looked straight ahead and took notes on a legal pad during Flemmi's testimony and did not appear to look at him.

In one of the slayings he recounted, Flemmi said he and Bulger sprayed a phone booth with gunfire in 1975, killing bar owner Edward Connors, because he was "telling people Winter Hill business," including details about an earlier murder committed by the gang.

Flemmi said another member of the gang had lured Connors to the phone booth by telling him he would receive a call there at a certain time. Bulger and Flemmi were waiting for him, Flemmi said.

"We just stepped out from the side of the building — the garage — and shot him," Flemmi said, matter-of-factly. "We just fired on him."

Flemmi said Bulger emptied a double-barreled shotgun and a pistol, while Flemmi fired seven or eight shots.

As for the strangling of his girlfriend, Flemmi said he initially refused to go along with Bulger's plan to kill Davis, whom he had been dating for years.

He said Bulger gave a litany of reason she had to die, saying among other things that he was worried because Davis was flashing around gifts Flemmi had given her, including a Mercedes and expensive jewelry. "That was drawing attention to me and to him," Flemmi said.

He said Bulger told him to bring Davis to a house Flemmi had bought in South Boston. As soon as they walked in, Bulger grabbed her by the neck and strangled her as he carried her downstairs, Flemmi said.

Flemmi said he laid her body on a tarp, and Bulger "went back upstairs and he laid down." Two associates came and put the body in the trunk of a car, and she was buried along the banks of the Neponset River in Quincy.

Bulger, 83, is accused of playing a role in 19 killings.

Flemmi, 79, pleaded guilty in 10 killings and was sentenced to life in prison in a deal with prosecutors that spared him the death penalty for murders in Oklahoma and Florida.

Flemmi also provided more detail on the gang's corrupt relationship with former FBI Agent John Connolly, who was eventually convicted of tipping off Bulger and Flemmi ahead of a 1995 indictment.

Bulger fled Boston and was one of the nation's most-wanted fugitives for more than 16 years until he was captured in Santa Monica, Calif., in 2011. Flemmi was arrested and has been in prison ever since.

Flemmi said he and Bulger fed Connolly information on the Italian mob. At the time, taking down the Mafia was a top priority for the FBI.

Flemmi said the gang also regularly paid Connolly and other FBI agents for tipping off the gang about investigations. He said the gang gave Connolly about $230,000 in cash during a 15-year relationship.

In 1983, Connolly received two $25,000 payments, Flemmi said. After receiving the second payment, Flemmi said, Connolly remarked, "I'm one of the gang."

Flemmi said the gang also paid cash to five other Boston FBI agents, repeating testimony he gave in other trials.

He is set to return to the witness stand Monday.

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