If anyone has a clue where he is, it's Kevin Weeks. For 20 years, he was Bulger's right-hand man, and the last person known to have seen him in the United States.
But six years ago, Weeks turned on his boss, becoming one of the most important witnesses ever against organized crime.
Weeks, who has written his story in a book called "Brutal," talks to correspondent Ed Bradley; it's a story about murder, mayhem and treachery and it's told by the keeper of Whitey Bulger's darkest secrets.
Kevin Weeks is a soft-spoken, 49-year-old native of South Boston. But don't be fooled by the low-key, matter-of-fact way he answers questions about his life of crime.
Weeks readily admits he has committed a laundry list of crimes, including beating people up, shooting and stabbing people, helping kidnap people and being an accessory to murder. It's quite a resume.
"It's the business we were in," Weeks tells Bradley.
The business they were in was organized crime. And what set Whitey Bulger's organization apart was its penchant for violence. Weeks says it was all part of the folklore of this Irish, working-class neighborhood known as "Southie."
Growing up in Southie, Kevin says one had to fight. "You didn't have to win, but you had to fight," he says.
On these streets, Whitey Bulger was a known as a vicious gangster who never hesitated to use violence. Weeks, who had a reputation as a tenacious street fighter, caught the crime boss's eye while he was working as a bouncer at a local bar. Over the years, he became Bulger's most trusted confidante.
Asked what his job was working for Bulger, Weeks says, "Anything he asked me to do."
Including murder. For 20 years, Weeks was with the crime boss nearly every day. But they were exceedingly careful. There are only two known photographs of them together. One photo was taken at a park called Castle Island, where they talked business out of earshot of police bugs. Weeks says the man he called "Jimmy" was a criminal mastermind.
"Ninety-eight percent of his waking hours was dedicated to crime, two percent to pleasure. He was very disciplined. Had no bad habits. He didn't drink. He didn't gamble. Didn't do drugs," says Weeks.
No bad habits, if you don't count murder. And killing was something Weeks says Whitey thoroughly enjoyed.
Asked how Bulger killed people, Weeks says: "He stabbed people. He beat people with bats. He shot people. Strangled people. Run 'em over with cars.
"After he would kill somebody, it was like a stress relief. You know? He'd be nice and calm for a couple of weeks afterwards. Like he just got rid of all his stress."
Weeks told 60 Minutes he helped Bulger commit three murders in one house. He lured the victims there, stood guard over them while they were interrogated, and after they were killed, he buried them in the basement. One of the victims was a gun-runner named John McIntyre, who was cooperating with police.
"John McIntyre was originally strangled. But the rope was too thick. So he was gagging. So Jimmy shot him in the head. And then pulled his teeth. And we buried him," Weeks recalls.
Weeks says the teeth were pulled because at the time there were dental records but no DNA. It was an attempt to keep victims from being identified.
Asked if he has any regrets about the loss of life he is responsible for, Weeks says no.
If he has any regrets, it is about one person he didn't kill. Howie Carr is a columnist for the Boston Herald, as well as a radio talk show host, who has been a thorn in the side of Whitey Bulger and his gang for 20 years.
"Whitey Bulger is a serial killer, cocaine dealer, bank robber, pedophile, very smart criminal," says Carr.
"Did you consider him a worthy adversary? I mean, is that why you went after him so hard?" Bradley asked.
"I went after Whitey just because I couldn't believe he was getting away with what he was doing, and that nobody would write about it," Carr explains.