Peter Von Frantzius was one of Chicago’s most famous guns suppliers,provided the guns which later were found in Fred Burke's possession
He sold Thompson submachine guns legally at that time. But, one of the consequences of the St. Valentine's Day Massacre was passage of the National Firearms Act of 1934, which outlawed private ownership of machine guns and sawed-off shotguns.
The Thompson was developed during WWI as a "trench broom"--a soldier, if he made it across "no man's land" to the enemy trench, could stand at the end of the trench and "sweep" the enemy with fire, instead of jumping into the trench and fighting one on one with bayonet, rifle butt or fists. But, the armistice was signed before a single Tommy gun got overseas. And, there was scant interest in it by armed forces or law enforcement agencies. So, Auto Ordnance took to selling them to private individuals. One of the most famous magazine ads of the Twenties shows a Western rancher, in big hat and chaps, using a Tommy gun hold off a band of mounted, masked rustlers.
