BOSTON (Reuters) - A former New England mob boss and an associate in 1993 murdered a Boston nightclub manager they suspected of cooperating with investigators, a federal prosecutor said on Wednesday at the start of their trial.

George Kaufman, stands with Frank "Cadillac" Salemme (R), in an U.S. government surveillance photo from early 1990s provided by the U.S. Attorney's Office in Boston, Massachusetts, U.S., on May 8, 2018. Courtesy U.S. Attorney's Office/Handout via REUTERS

Frank “Cadillac” Salemme, 84, and Paul Weadick, 63, participated in the slaying of Steven DiSarro, Assistant U.S. Attorney Fred Wyshak told jurors in Boston federal court. DiSarro’s remains were found two years ago.

Wyshak said that Salemme confessed while talking to Stephen “The Rifleman” Flemmi to killing DiSarro. Flemmi is an associate of Salemme and James “Whitey” Bulger, who for a quarter of a century ruled Boston’s criminal underworld and is now serving life in prison.

Flemmi “will tell you Frank Salemme told him they killed Steve DiSarro because they thought he was weak,” Wyshak said in his opening statement.

Defense lawyers countered that Flemmi, who is serving a life sentence for 10 murders, could not be trusted.

Steven Boozang, Salemme’s lawyer, said Salemme long ago confessed to eight murders after agreeing to testify against a corrupt agent of the Federal Bureau of Investigation, yet he has consistently denied killing DiSarro despite the potential to get a “free pass.”

“Just because he’s done these bad things doesn’t mean he’s done this,” Boozang said.

According to prosecutors, Salemme, a hit man who by 1990 had emerged as the head of the Patriarca crime family in New England, had a secret interest in a South Boston music venue called The Channel, which DiSarro had purchased.

In 1993, an FBI agent told DiSarro he would soon be indicted and should cooperate with authorities who were probing Salemme and his now-deceased son, Francis Salemme Jr., prosecutors have said.

Wyshak said Flemmi - who is expected to testify - witnessed Salemme Jr. strangling DiSarro at Salemme’s home on May 10, 1993 as Weadick held his legs off the ground and Salemme watched.

Flemmi soon left, but Salemme told him they killed DiSarro, Wyshak said.

Salemme pleaded guilty in 2008 to obstructing justice by providing false information to investigators suggesting others might be responsible for DiSarro’s death.

Due to his cooperation with authorities, Salemme was placed in the federal witness protection program and lived in Atlanta under an alias.

After DiSarro’s remains were discovered behind a mill in Providence, Rhode Island, prosecutors say Salemme left his home in July 2016 without notifying the U.S. Marshals Service as required. He was arrested in Connecticut that August.

(Edits third paragraph and adds dropped words “left his home” in last paragraph.)