Starting out as a low-level member of the St. Louis gang known as the Egan's Rats, Brothers soon graduated into labor racketeering and contract murder. Dodging a 1929 murder indictment, Brothers fled to Chicago, where he found work in the Chicago Outfit, under the notorious crime Czar, Al Capone. Leo was ultimately convicted of the Lingle murder, being sentenced to fourteen years. Most observers, then and now, believe that Brothers was handed up to the state by Al Capone as a sacrifice.
After his release in 1940, Brothers returned to St. Louis, beat his original murder case, and became hooked up with the local mob. Three months after an abortive attempt on his life, Leo Brothers died of heart disease in St. Louis on December 23,1950.