This courtroom sketch depicts Stephen "The Rifleman" Flemmi testifying at the trial of James "Whitey" Bulger. (Photo: Margaret Small, AP)

BOSTON -- Stephen "The Rifleman" Flemmi testified Monday that alleged mob boss James "Whitey" Bulger killed two men himself 1982.

Bulger shot Brian Halloran and Michael Donahue as they were driving away from a waterfront restaurant, Flemmi said. Flemmi wasn't present, he said, but he heard Bulger take credit later that night. His testimony corroborates what witness Kevin Weeks said earlier in the trial.

Bulger, 89, is on trial for murder and racketeering.

Flemmi, Bulger's former partner and friend, also provided new detail about the extent and nature of Bulger's activity as an FBI informant. According to Flemmi, Bulger lied to his corrupt FBI source, John Connolly, by falsely pinning the Halloran and Donahue murders on rival gang members, as well as Boston's Italian mafia and Jack McCormack.

In misleading the FBI, Bulger "was taking the heat away from himself," Flemmi said. Bulger's gang had been a focus of investigation after the Halloran murder, Flemmi said.

Bulger denies ever having been an FBI informant.

Flemmi, 79, on Friday had described Bulger's alleged role in a string of killings during the 1970s and '80s. He said Bulger either planned the killings, approved them or committed them himself. Bulger looked straight ahead and took notes on a legal pad through the testimony.

Bulger, the alleged former leader of the Winter Hill Gang, fled Boston in 1994 and became one of the nation's most wanted fugitives. He was captured in 2011 in Santa Monica, Calif., where he had been living with his longtime girlfriend in a rent-controlled apartment.