Several months ago, I received an email out of the blue from a man named Thomas Worsdale. It seems that “Man With the Sawed-Off Leg” had provided a key bit of family history. Mr. Worsdale said his cousin had tipped him off to the New Yorker story about the Rubel robbery and The New York Times article I had written about the Riverside Drive townhouses that included the story of the heist. He also learned about my book, bought a copy and read it, concentrating especially the parts about Bernard McMahon, the Irish gangster who helped mastermind the robbery.

“You see, Bernard McMahon is my great-uncle,” Mr. Worsdale wrote me. “We had always been told that he may have been involved in the Irish Mob and criminal activity in NYC, and we were told he died either in a car accident or a shooting.”

I spoke to his cousin, Marion Shanahan, who recounted similar impressions. She had heard Uncle Bernard just disappeared from family after 1930. The story she knew was that he died a violent death of some sort, perhaps for crossing the mob. One version had his body delivered to his mother’s doorstep rolled up in a carpet.

But how could I be sure that their Uncle Bernard was my Bennie the Bum, the mobster? Bernard McMahon is not exactly an uncommon name. I dug deeper and became convinced they were one in the same for the following reasons.

1. Gangster Bernie used the names Dalton and Murray as aliases. The cousins told me that their great-uncle had a brother-in-law named Dalton and that a brother housed a lodger named Murray.
2. Records for Uncle Bernie and Gangster Bernie put them in the same neighborhoods during the same years, and the 1915 census listed the uncle’s address as 439 W. 24th St., the same given to McMahon in news reports about the shooting of a jeweler.
3. McMahon’s body in the Rubel story was identified in the morgue by a brother named John. Uncle Bernie had a brother named John.
4. Photographic evidence.

Here is a picture of Uncle Bernie, provided by Mr. Worsdale, working as a bartender probably in his father’s tavern.

Here is mugshot of gangster Bernie

Look at the curve of the nostril, the cleft chin, the shape of the lips, the haircut (the only difference is that the part is on different sides; maybe one of the images was somehow reversed?) They are clearly the same man.

Thanks to Mr. Worsdale and Ms. Shanahan, some details of Bernard McMahon’s life have been fleshed out. Bernard was 5-foot-9, slender, blond and blue-eyed. He had two sisters and two brothers, dapper men who worked on the docks, in the fish market, behind the bar or behind the wheel. “The McMahons were an interesting family in that they stuck together through thick and thin,” Ms. Shanahan said.

Bernard’s parents came from County Monaghan in Ireland. His father, also Bernard, was injured in a trolley accident in 1919 and died in 1923. The accident led to a lawsuit which yielded the family several thousand dollars.