CNN  — 

In a 3-foot grave near a river not far from Boston, Paul McGonagle’s body lay decaying, undisturbed until his remains were found nearly 20 years ago. Parts of a pelvic bone. A fractured skull with decomposed brain matter. A ring with a part of a decomposed finger bone.

McGonagle was the leader of a gang that was a rival to reputed Irish mobster boss James “Whitey” Bulger’s Winter Hill Gang. Bulger was suspected of being involved in McGonagle’s death in 1974, and in 18 other mob-related killings between 1973 and 1985.

Whenever Bulger drove by the shallow grave, he would say “Drink up, Paulie,” a witness testified at Bulger’s trial in 2013. A federal jury convicted Bulger of 31 counts that year, including racketeering and extortion, and found him culpable in 11 killings, including McGonagle’s death.

Bulger, leader of the South Boston gang, was the ruthless kingpin of a criminal empire that a federal judge said committed “unfathomable” acts. His infamous reign would be the inspiration for Jack Nicholson’s character in Martin Scorsese’s film “The Departed.” Bulger evaded police for 16 years before his capture in 2011.

He died Tuesday in a West Virginia prison, an 89-year-old man serving two life sentences and five years.

“The guy is a sociopathic killer,” Tom Foley, the former Massachusetts State police head who spent years trying to capture Bulger, told CNN in 2011. “He loved that type of life. He’s one of the hardest and cruelest individuals that operated in the Boston area. He’s a bad, bad, bad guy.”

Bulger, a longtime FBI informant, was killed in the US Penitentiary Hazelton in Bruceton Mills. He was found unresponsive at 8:20 a.m., according to statement from the Federal Bureau of Prisons.

He was pronounced dead by the Preston County medical examiner after life saving measures failed. No other inmates or staff were injured, the prisons bureau said.

The FBI is investigating Bulger’s death, which occurred a day after he was transferred to the West Virginia facility, the prison bureau said.

‘It’s a happy day’

A statement Tuesday from Andrew Lelling, the US Attorney for Massachusetts, was brief. It made no mention of Bulger other than he had died.

“We received word this morning about the death of James “Whitey” Bulger. Our thoughts are with his victims and their families,” the statement said.

The brother of a woman Bulger was accused of killing in 1981 told CNN, “It’s a happy day.”

Steven Davis’ 26-year-old sister, Debra Davis, was the girlfriend of Bulger partner Steve “The Rifleman” Flemmi. Flemmi testified that he lured Davis to a house where Bulger strangled her. Flemmi testified he “inadvertently blurted out” to Davis that he and Bulger were FBI informants, and that Bulger said several times “he wanted to kill” Davis because she knew about the relationship with the FBI.

The defense presented testimony from former hitman John Martorano, who admitted he “accidentally strangled” Davis. Martorano served 12 years in prison, but was released in 2007 in exchange for testifying against Bulger.

The jury had “no finding” in Davis’ death. Bulger “didn’t have the right to live as long as he did,” her brother said.

The end of a ’16-year honeymoon’

In 1995, Bulger skipped town ahead of a pending indictment, allegedly on a tip from a rogue FBI agent.

The mob boss, who took Osama bin Laden’s place at the top of the FBI’s Top 10 Most Wanted list, hid in plain sight in Santa Monica, California. He and his girlfriend, Catherine Elizabeth Greig, lived blocks from the beach under the aliases of Charlie and Carol Gasko. The fake name was even on the door bell list.

The couple dined some nights at a white-tablecloth establishment that drew Hollywood producers, sitting in a corner table in the patio at the back of the restaurant, a manager said. They were generally polite, too. Bulger often wore a hat, with the brim pulled down, neighbor Catalina Schlank told CNN in 2011.

“They were kind of secretive. Even on the phone – you couldn’t call them,” she said. “Sometimes, I wanted to give them a tip of stuff on sale.”

A tip led the authorities to him.

In 2011, the FBI lured a likely unsuspecting Bulger out of his seaside apartment. Bulger had received a phone call and was told that his lockbox had been broken into in the basement parking lot area of his building. The FBI arrested Bulger when he went to check it out, a source told CNN.

Bulger would refer to his years as a fugitive with Greig as a “16-year honeymoon.”

In 2012, Greig was sentenced to eight years in federal prison for identity fraud and helping Bulger avoid capture.

During Bulger’s trial, gruesome details emerged about the deaths he was accused of being involved in.

Onetime enforcer Kevin Weeks testified how Bulger killed Arthur “Bucky” Barrett.

In the summer of 1983, Bulger organized a meeting with Barrett under the guise that he had stolen diamonds he wanted to get rid of. When Barrett showed up at the house, Weeks, Bulger and Flemmi were waiting.

They chained Barrett to a chair. For hours, they grilled him about a rival gang and local drug dealings, Weeks testified.

Barrett tried to buy his way to out, telling Bulger about his stash of $40,000.

Weeks said Bulger left the house to pick up the money while he and another associate watched Barrett. When Bulger returned, he told Barrett to walk down to the basement. Then Bulger put a gun to the back of Barrett’s head and pulled the trigger, according to Weeks.

“Nothing happened,” Weeks said.

Bulger realized the gun’s safety was on. He removed the safety and shot Barrett, Weeks said.

‘It’s just sad that it took so long’

During his sentencing, Bulger did not make eye contact with the relatives of the people he killed, nor those slain by his accomplices in the Winter Hill Gang.

He was a convicted murderer in his 80s. He was likely going to die in prison.

Carmen Ortiz, the former US Attorney for Massachusetts who oversaw Bulger’s prosecution, said she hopes Bulger’s notoriety didn’t take away the focus from his victims. Ortiz says she hopes his death “is the end of a very sad chapter in Boston’s history, during which this man caused so much harm to many through his brutal crimes.”

“He had it coming to him and it’s just sad that it took so long,” Steven Davis said.

CNN’s Ray Sanchez, Laura Ly, Kristina Sgueglia and Ann O’Neill contributed to this report. Michael Martinez and Laura Batchelor also contributed to this report.