James "Mad Bomber" Belcastro (1895 – August 23, 1945) was a Black Hand gang member, extortionist, and later chief bomber for the Chicago Outfit during Prohibition.
Known as "King of the Bombers", Belcastro was highly skilled at constructing improvised explosive devices. He used these skills to extort money from business owners in Chicago's Little Italy district during the 1910s. In the early 1920s, Johnny Torrio and Al Capone formed the Chicago Outfit and put the Black Hand gangs out of business. However, Capone invited Belcastro to join the Outfit and he soon became a prominent member. During the mid to late 1920s, Belcastro was suspected of causing over 100 deaths while bombing saloons that refused to buy alcohol from Capone. Wikipedia