John M. Larn, cowboy, rancher, sheriff, and outlaw, was born in Alabama on March 1, 1849. He killed a rancher in Colorado before drifting to Fort Griffin, Texas, about 1869, and probably killed a sheriff near Santa Fe. In 1871 he signed on as foreman of Bill Hays's cattle drive to Trinidad, Colorado. On the trail, Larn is alleged to have killed two Mexicans and a shepherd. The first known allegations against him for cattle stealing surfaced in 1873. That year, Larn, accompanied by a posse and thirteen soldiers from Fort Griffin, ambushed and killed all members of Bill Hays's cattle outfit near Bush Knob in Throckmorton County. Larn had a warrant charging the men with rustling cattle. In 1874 he joined the Tin Hat Brigade in Griffin. This vigilance committee saw to the protection of the lives and property of the people in the surrounding area. The band worked swiftly, and many a horse thief was found hanging from a tree near the river. The respect Larn gained as a member of this group helped get him elected sheriff of Fort Griffin in 1876, a position he held for less than a year. By 1876 he had built a house at Camp Cooper Ranch on the Clear Fork in Lambshead.
After his resignation as sheriff in March 1877, Larn and one of his associates, John Selman, were appointed deputy inspectors of hides for Shackelford County. They were to inspect all cattle herds entering and leaving the county and to supervise butchers. The same year they also secured a contract to supply the soldiers of the fort and the Tonkawa Indians with beef. Three cattle a day were supplied to the quartermaster at the fort. The ranchers in the area began complaining, however, that they were losing cattle, while Larn's herd was not diminishing. The Grangers were also reporting acts of violence. A band of men, reportedly led by Larn and Selman, were bushwhacking them, driving off their cattle, shooting down horses on the open range, and firing shots in the dark at the homes of terrified citizens. In February 1878 a posse of civilians secured a warrant to search the river behind Larn's house for hides. Six hides not belonging to him were recovered; Larn was arrested and taken to Fort Griffin, then released. Still, violence in the area continued. On the morning of June 23, 1878, Larn was arrested in his barn by Sheriff William R. Cruger. He was taken to the Albany jail, where in the early morning hours of June 24 he was fatally shot by a group of masked men. His body was returned to Camp Cooper Ranch, and he was buried beside his infant son. Larn was married to Mary Jane Matthews in 1872, and they had two sons.