Deputy Sheriff Charles Nichols has a dubious distinction—the first Dallas County (TX) lawman to die in the line of duty, back in January 1871. The incident is noted for another fact: one of the shooters was the youngest Younger brother, John (photo).
Details are sketchy, but all of the participants supposedly were drinking. Younger and a compatriot entered a store where Nichols and a pal were eating, and an argument ensued. The guns went off; Nichols and his friend were killed. The two outlaws escaped and were never tried.