Johnson's criminal career began when he was only nine years old, when he was arrested for stealing money out of a cash register at Helen's Candy Store, which was Murder, Inc. mob hangout.

As a result of this accident, Johnson sustained head injuries that would plague him with persistent headaches for the rest of his life.

Allan May, quoting from the memoir of Retired NYPD Lieutenant Remo Franceschini of the Queens District Attorney's Squad, describes Johnson thus:[2] He was real stocky, about five feet nine inches and well over two hundred pounds, looked like a professional wrestler.

You didn't want to meet Willie Boy on the street, and if you met him you'd better have backup ammunition in your pocket because six bullets were not going to stop this guy.

His caporegime, Carmine Fatico, vowed to financially support Johnson's wife and two infant children but soon broke this promise.

Johnson rarely volunteered information but would answer direct questions asked by law enforcement officials.

In 1978, Johnson informed Boland about the whereabouts of Lucchese crime family capo, Paul Vario's, hijacking headquarters, which at the time was operating out of a scrapyard owned by Clyde Brooks.

He did, however, make some profit; his information solved a number of major hijackings for the FBI, and in cases where insurance companies offered large rewards for recovery of stolen goods, the FBI provided confidential affidavits attesting that Johnson was directly responsible for recovery of hijacked goods.

However, as his FBI handler, Special Agent Martin Boland, noticed, Johnson refused to discuss his background or childhood in any detail.

Johnson also provided the FBI with information on a largescale narcotics ring, run by John Gotti and others, called the "Pleasant Avenue Connection"; revealed that Gotti and Angelo Ruggiero had murdered Florida mobster Anthony Plate; and gave details on the murder of James McBratney, the man who kidnapped Emanuel Gambino.

In a public hearing that year, Federal prosecutor Diane Giacalone revealed that Johnson was working for the FBI, in an attempt to convince him to plea bargain and testify against Gotti.

Johnson's FBI handlers tried to convince him to enter the Witness Protection Program, but he refused, and publicly denied being an informant.

On August 29, 1988, Bonanno family hit men, Thomas Pitera and Vincent "Kojak" Giattino, allegedly ambushed Johnson in front of his Brooklyn home as he walked to his car and shot him to death.

[5] In 1991, Pitera had accused Johnson of the 1980 murder of John Favara, the man who accidentally struck and killed Gotti’s 12-year-old son with his car.