One prominent Chicago loan shark known as King Solomon aka Nenos Solomon who used to work as collector for the DeStefano brothers, said that Mario was more evil than his brother Sam. If that's true then god knows what Mario really looked like when he was nervous or angry at someone.

As additional info, here's DeStefano's loan sharking crew during the early 1960's...

Crew leader: Sam DeStefano

Members: Mario DeStefano, Pete Cappelletti, Tony Spilotro, Art Pascucci, Sam Gallo, Al Zaccagnini and Chuck Crimaldi.

There are also some indications that this crew was overseen by Charles Nicoletti.