Some neighbors of a former mob hit man were shocked to learn about his past during his testimony against James "Whitey" Bulger this week.

John Martorano has admitted to 20 killings and previously spent 12 years in prison in exchange for his cooperation with authorities.

He lives in a condo on a golf course in Milford, Mass. Neighbors say they didn't have a clue about his past until seeing him on television in connection the racketeering trial in Boston.

One vowed never to get into any arguments with Martorano in the future, adding: "Whatever he says, he's right."

But the town's police chief says the 72-year-old's only interaction with local authorities was a written warning after a minor fender bender last year.