BOSTON  -- A prosecutor called reputed gangster James "Whitey" Bulger "one of the most vicious, violent and calculating criminals ever to walk the streets of Boston" as he urged a jury Monday to convict Bulger of charges that include 19 killings committed during the 1970s and '80s.

Federal prosecutor Fred Wyshak, who pursued a case against Bulger for more than two decades, recounted gruesome details of the killings. Among the victims, he told the jury, were two men who were chained to chairs for hours, interrogated, then shot in the head, two women who were strangled, and two men who died in a hail of gunfire as they left a South Boston restaurant.

Wyshak said Bulger, as the boss of the Winter Hill Gang, South Boston's Irish mob, was a hands-on killer who committed many of the killings himself and orchestrated others.

He described the gang's array of guns, knives, a souped-up "hit car" and walkie-talkies used when the group decided to kill someone.

"They hunted their targets," Wyshak said. "These men didn't hunt animals, ladies and gentlemen, they hunted people."

Wyshak spoke for more than three hours. Bulger's defense lawyers were scheduled to give their closing argument Monday afternoon.

During the nearly eight-week trial in federal court, jurors have heard sometimes grisly testimony about the 19 killings in which Bulger is accused of participating and numerous instances of extortion, money laundering and hoarding of guns.

Prosecutors say Bulger, 83, was secretly working as an FBI informant during the same period - a claim his lawyers have strongly disputed.

He fled Boston in 1994 after being tipped off by a retired FBI agent ahead of his indictment and was one of the FBI's most-wanted fugitives until he was captured with his longtime girlfriend in Santa Monica, Calif., in 2011.

Wyshak will have to convince the jurors they can believe at least some of the testimony of three key witnesses against Bulger. All are gangsters-turned-informants who admitted committing heinous crimes, including murder, and struck deals with prosecutors to testify against him.

Bulger's lawyers have spent much of their time disputing allegations he was a "rat" who informed on the rival Italian mob and people in his own gang. The defense also tried to counter allegations Bulger strangled two women - something he apparently considered a violation of his underworld code of honor.

The jury is expected to begin deliberations Tuesday.

Bulger's girlfriend, Catherine Greig, pleaded guilty last year to charges related to helping him stay on the run and was sentenced to eight years in prison.