February 14, 1929, went down in history as the day that love gave way to violence in Chicago. On that date, which in the United States is celebrated as Valentine's Day, the famous gangster Al Capone ordered a brutal attack against his rivals from the North Side gang, led by Bugs Moran. Capone's goal was to eliminate competition in the lucrative business of smuggling alcoholic beverages, prohibited by Prohibition.

Capone's plan was hatched by his right-hand man, Jack McGurn, who enlisted the help of local and out-of-town gunmen. They set up an ambush at the SMC Cartage Company garage, where Moran's men were waiting for a shipment of whiskey from Detroit. At around 10:30 in the morning, two cars stopped in front of the garage and four men got out, two of them dressed as police officers. They entered the garage and took over the seven men inside, making them stand with their backs against the wall. Then the other two men, who were wearing overcoats, took out their Thompson submachine guns, known as Tommy Guns, and opened fire on the prisoners. More than 100 shots were fired, leaving the bodies riddled with bullets. The fake police officers then left the garage escorting the other two shooters, as if they were going to arrest them. They got into their cars and fled, leaving no trace.

The victims of the massacre were six members of Moran's gang: Frank and Peter Gusenberg, Albert Kachellek, Adam Heyer, Albert Weinshank and John May. The seventh dead was Reinhardt Schwimmer, an optometrist who liked to get involved with criminals. The only survivor was John May's dog, who was in the garage at the time of the shooting. Interestingly, Capone's main target, Bugs Moran, narrowly escaped death. He was on his way to the garage, but he was late and saw the police cars arriving. He then hid in a nearby store and avoided the massacre.

The St. Valentine's Day massacre shocked public opinion and the press, which widely publicized photos of the bodies at the crime scene. The case also increased pressure on authorities to combat organized crime in Chicago. Al Capone, who was in Florida at the time of the massacre, denied any involvement and was never charged with the crime. However, he was arrested in 1931 for tax evasion and sentenced to 11 years in prison. He died in 1947, aged 48, from a cardiac arrest. Jack McGurn, the mastermind of the massacre, also escaped justice, but was murdered in 1936 by an unknown gunman. The St. Valentine's Day massacre was one of the bloodiest episodes in the history of the American mafia.