Many folks are not well informed about the days of the "automobile bandits", roughly 1930 to 1940. Cities and towns throughout the Midwest and southwest states were plagued by armed gangs arriving by automobile and looting entire towns, usually armed with automatic weapons.
Many communities erected fortified bunkers manned by local police armed with Browning Automatic Rifles and Thompson Submachineguns, usually located in town squares or at highway access points. Occasionally effective in stopping or deterring such assaults, there were also a number of horrific incidents of engagement with completely innocent parties.
During the days of very limited telephone or telegraph communications it was difficult to deal with such assaults. Local populations were terrified and frequently relied upon volunteer guards or irregular militia units for protection. If a message was received that Bonnie & Clyde, or Pretty Boy Floyd, or any number of other desperados were in the area, or had struck other towns in the vicinity, it wasn't unusual for entire communities to go into "lockdown" mode for days.
Local law enforcement was minimal in staffing, training, equipment, and every other means of dealing with organized gangs. National Guard armories, VFW posts, and other assets were relied upon for local defense. J. Edgar Hoover, Melvin Purvis, and the G-Men were in a totally responsive and defensive mode, usually able to respond only days after an assault.
The effects of the Great Depression (massive unemployment, widespread dislocation of populations, general dissatisfaction with government in general) coupled with the lingering effects of Prohibition, and other factors created an environment in which many young people saw criminal activity as the only possible means of getting ahead in life (not unlike today in many urban settings). Gangsters, by design or by reputation, built huge followings (even without FaceBook or internet connections), and cheerleading crowds were not uncommon (especially for those like Bonnie & Clyde, who liked to rip through bank vaults and burn mortgage papers to ingratiate themselves with local farmers and small business owners).
An interesting period in American history, and not without modern parallels.