Wilber Underhill and his murderous gang of the mid to late 1933 era, is a group you don't hear much about today being overpowered in the media by the likes of Dillinger and the others.  Underhill and his gang's exploits were portrayed in a book by Ron Morgan titled, "The Tri-State Terror; The Life And Crimes Of Wilbur Underhill if you're interested. (Morgan is one of the foremost experts on Oklahoma law enforcement history.)
 
Note:  The spelling of "Wilber" above is taken from his sister's letter.

Underhill met his demise in a blazing shootout in the dust bowl of Shawnee, OK in December, 1933 and a further look into the players present gives you some of the first photos of those involved from law enforcement.  Namely (prior to joining the Bureau) "Jelly" Bryce and Clarence Hurt who were Oklahoma Detectives at the time.  A classic photo of Bryce, Hurt, SAC Ralph Colvin, SA Paul Hansen and SA Kelly Dederick exists portraying all of them hold Thompsons outside the shootout house location. (note: long before the May/June gun legislation for the Bureau in 1934).

One Bureau Agent present with others at the Shawnee, OK shootout was SA George Franklin whose son, George, Jr., now living in Albuquerque, N.M., has been in contact with me recently.

SA Franklin, whom you never hear about today either, was clearly one of those 30's Agent pioneers of the time assigned to Oklahoma. In fact, SA Franklin was extremely close to "Jelly" Bryce from the son's accounts and family photos.  
 
Page 1 of Dorothy Underhill's letter to SA Franklin is here
 
Page 2 is here
 
Page 3 is her open letter to the citizens of Joplin, Mo.