At this spot, on Nov. 27, 1934, two federal agents and two professional criminals fought what may have been the most savage gunfight in American history, short of military combat. Of the four, three had automatic weapons, the fourth a short-barreled, semi-automatic 12-ga. riot gun, plus assorted handguns of the .38 Super and .45 ACP variety. All that firepower means that it was certainly more intense than the fabled “Gunfight at the O.K. Corral,” fought with single-action revolvers and one double-barreled shotgun; it was probably more intense (though it’s a tough call) than the FBI Dade County shootout of 1987 where no automatic weapons were involved, only one semi-automatic rifle (a Mini-14), one short-barreled pump shotgun and the rest duty handguns.
A Battle At Barrington: The Men & The Guns – by Stephen Hunter

When you combine Stephen Hunters ability to write a good story with the research of an actual event, you get a piece of writing of this magnificent caliber.

He has a great book titled American Gunfight: The Plot to Kill President Truman–and the Shoot-out That Stopped It .  It is a little known event and we were so very close to another presidential assassination. How close? One look up. Take a chance to read the book.