Irish-American gangster Charles Dion O'Bannion, nicknamed "Deanie", was, unlike many of his fellow contemporary gangsters, born and raised in the US. From the small Illinois town of Marca, his family moved to Chicago after his mother's death in 1901, settling in an Irish neighborhood on the city's North Side.
O'Bannion's childhood friends included future gangsters Hymie Weiss, George Moran--aka "Bugs Moran"--and Vincent Drucci (aka "The Schemer"), all members of an Irish strongarm robbery crew called The Market Street Gang. The gang came into its own during the infamous Chicago newspaper wars, in which the city's competing newspapers hired gangs of thugs to beat up business owners who didn't sell their paper or newspaper boys who sold the competition's paper. O'Bannion graduated from beating up newspaper boys to safecracking--for which he was eventually arrested--and drugging patrons' drinks in the dives he worked at, after which he and his gang would rob them when they passed out.
O'Bannion was still a small-time hood when Prohibition came into effect in 1920, and it was then he found his calling. He began by smuggling beer, whiskey and gin from Canada to the US, and was extremely successful at it. He built his own outfit, known as The North Side Gang, and made huge amounts of money supplying the wealthy Chicago area called the Gold Coast, along the lakefront, with illegal liquor. He still kept his hand in the strongarm business, however, and his mob became infamous for hijacking the trucks of rival bootleggers, beating up or killing the drivers and taking their loads. When he married in 1921, he indulged his passion for flowers--and got himself a legitimate front for his rackets--by buying a flower shop, which eventually became the main supplier of floral arrangements for the funerals of many of the gangsters killed in the city's internecine mob wars.
Italian gangster Johnny Torrio had called a meeting of Chicago's bootleggers in 1920 to divide up the city and put a stop to the bloody battles among the various gangs. O'Bannion attended the meeting and was awarded the North Side territory, including the very profitable Gold Coast section, in exchange for supplying the Torrio gang with muscle in its effort to ensure that their candidate won the election for mayor of nearby Cicero, thus ensuring a haven from which they could run their organizations without fear of prosecution.
The "agreement" only lasted for a few years before O'Bannion started chafing under Torrio's control. In addition, the city of Cicero had become a virtual gold mine for Torrio since he assumed control of it, and O'Bannion wanted in. Torrio mollified him by giving him a strip of the city in which to establish his speakeasies. O'Bannion used that to persuade other Chicago speakeasy owners to move their operations to his Cicero fiefdom, to which Torrio took strong offense, but O'Bannion refused Torrio's order to stop bringing in new speakeasies. In the meantime, a family of brutally violent Italian bootleggers called the Gemma Brothers began moving into O'Bannion's Chicago territory, and his complaints to Torrio about them went unheeded. Infuriated, O'Bannion began hijacking the Gemma gang's trucks. The Gemmas decided to kill O'Bannion and wipe out his mob, but were stopped by the other Italian gangs, who did not want a full-fledged gang war bringing heat on them. The last straw, though, was when Torrio discovered that O'Bannion had double-crossed him on a liquor deal that had cost him more than $500,000. He finally gave the Gemmas the go-ahead to kill O'Bannion.
On November 10, 1924, on the pretense of buying flowers for a fellow mobster's funeral, gangster Frankie Yale and two compatriots visited O'Bannion's flower shop. As O'Bannion extended his hand to greet Yale, the mobster suddenly grabbed his arm with both hands and the two gunmen pulled out pistols and emptied them into O'Bannion. He died instantly.