The gang employed military-inspired tactics taught to them in prison by men such as Herman Lamm.
While Makley, Clark, and Pierpont extended their vacation by driving west to Tucson, Arizona, Dillinger left Florida on January 12 and met up with Hamilton in Chicago at noon on January 15, a meeting that had been arranged between the two men while Dillinger was in Daytona Beach.
Later that afternoon they robbed the First National Bank in East Chicago.
At approximately p.m., 10 minutes before closing time, Dillinger and Hamilton, and an unidentified driver, pulled up in front of the bank on Chicago Avenue on the wrong side of the street, facing east in the westbound lane, double parked, and exited the vehicle, leaving the driver to wait in the idling car.
Hamilton waited in the bank's vestibule, while Dillinger entered the main room of the bank.
The police had been put on high alert and suspected the Dillinger gang of involvement in the robbery of the Unity Trust And Savings Bank of $8,700 the day before.