Former Winter Hill Gang leader Howie Winter has died

Howie Winter, the longtime leader of Somerville’s notorious Winter Hill Gang and a former crime partner of James “Whitey” Bulger’s, died Thursday of a heart attack at his home in Millbury, according to his lawyer. He was 91.

While best known as one of New England’s most powerful underworld figures in the 1960s and ’70s, in recent years Winter had been quietly working behind the scenes, trying to help Boston’s Isabella Stewart Gardner Museum recover $500 million worth of artwork stolen during a brazen heist in 1990.

“I’m an art lover myself,” Winter told the Globe during an interview two years ago, detailing his efforts to locate and confidentially broker the return of the artwork by making overtures to dozens of thieves, wiseguys, and mob associates. “Everything was a dead end.”

On Friday, Anthony Amore, the museum’s security director, said Winter “acted in earnest to attempt to aide me in recovering our stolen artwork. I’ll miss that help.”

Winter’s death, he said, is “the true end of an era.”

During testimony in Bulger’s 2013 trial, Winter was implicated in a number of murders from the Irish gang wars of the 1960s and 1970s, including a young bartender who worked at a North End restaurant and was gunned down in 1973 in a case of mistaken identity. Winter was never charged with any of them, although he served time for fixing horse races at six East Coast race tracks, and drug trafficking.

“It’s the end of a legend, but not a good legend,” said Thomas Foley, a retired Massachusetts State Police colonel who investigated organized crime for decades. “He is a guy that actually got away with murder.”

The Somerville gangster was a throwback to a time when Boston’s dominant organized crime groups were the Mafia and the Winter Hill Gang — the so-called Irish mob, which was actually an amalgamation of Irish and Italian gangsters. The two groups controlled bookmaking and loansharking throughout the region, and though competitive, respected each other’s territory.

“The Mafia feared him,” Foley said of Winter. “They felt it was better to have a working relationship with him than take him on.”

Winter was born on St. Patrick’s Day in 1929, and served with the US Marines in World War II. He became leader of the Winter Hill Gang after his boss, James “Buddy” McLean, was gunned down in 1965 during the Irish gang wars. He met Bulger in the 1970s, when Bulger enlisted his help in resolving a bloody dispute between rival gangs in South Boston. Bulger became a lieutenant in the Winter Hill Gang, eventually teaming up with another member of the gang, Stephen “The Rifleman” Flemmi.

In 1979, federal prosecutors decimated the Winter Hill Gang with an indictment charging Winter and 20 others with a million-dollar horse-race-fixing scheme, but removed Bulger and Flemmi from the case because they were FBI informants. For that case and a separate conviction in state court for extortion involving pinball machines, Winter spent six years in prison. Bulger succeeded him as boss of the gang and later shifted the base of his criminal organization to South Boston.

In 1992, Winter was indicted on federal cocaine trafficking charges for arranging a drug delivery to a friend who was cooperating with the government. Prosecutors offered him leniency if he’d cooperate against his former associates, Bulger and Flemmi, but he refused and was sentenced to 10 years in prison.

“They wanted him to be a rat,” Winter’s attorney, the late Richard Egbert, said at the time. “Howie wouldn’t do it. He’s a man.”

Six years later, after the FBI publicly acknowledged during court proceedings that Bulger and Flemmi were longtime FBI informants, Winter said he had never suspected it. Still, he refused to cooperate against the pair.

Daniel Doherty, a retired Drug Enforcement Administration agent, said “a lot of evil passed through his hands,” but Winter was an “old school guy” who was respected for the way he conducted himself.

In 2012, Winter was indicted, along with an associate, on charges that he had tried to extort $35,000 each from two businessmen. The victims had loaned money to an attorney, who had difficulty repaying the money. Prosecutors alleged Winter threatened the men, but Winter claimed it was all a misunderstanding and he was actually trying to help the lawyer. As part of a plea agreement, Winter pleaded guilty to extortion and was placed on probation.

E. Peter Mullane, Winter’s attorney and longtime friend, said Winter wasn’t involved in “gratuitous violence,” but rather was embroiled in a clash between Irish gangs in the 1960s that was “violence to stay alive.”

“What he got tagged with publicly is not really representative of the person he was,” Mullane said. “He was generous and helped tons of people. He never said no when someone came to him for help.”

Winter’s longtime friend, James Martorano, a former Winter Hill Gang associate, said Winter was blamed for many things he didn’t do, and had also done a lot of good for people. “We all loved him,” he said. “It’s a big loss for us.”

Winter leaves his wife, Ellen, three daughters, and many grandchildren and great-grandchildren. A funeral Mass will be said Tuesday at 10:30 a.m. at St. Clement Church in Somerville. A wake will be held Monday from 4 to 7 p.m. at the George L. Doherty Funeral Home in Somerville.

Kevin Cullen of the Globe staff contributed to this report.