Sostenes l'Archevêque, one of the first badmen of the old Southwest, was the son of a French father and a Mexican-Indian mother and a great-grandson of an expatriate French colonist, Jean l'Archevêque. When Sostenes was a boy, his father was killed by an Anglo-American in the town of Sapello, in northeastern New Mexico. Sostenes reportedly vowed that when he grew up he would kill every gringo he met. Subsequently, he won considerable notoriety in the upper Rio Grande settlements as a cold-blooded gunfighter. By 1876, when he was finally run out of New Mexico, he was said to have killed twenty-three Americans, and his murderous actions had become unbearable even to his own Hispanic relatives.
L'Archevêque's sister was married to Nicolás (Colas) Martínez, a former Comanchero turned sheep rancher. Early in 1876 L'Archevêque accompanied the Martínezes and several other pastores to Oldham County, where they settled at Ventura Borrego's plaza, about a mile south of the Old Tascosa townsite. Apparently his reputation had preceded him; when Charles Goodnight, who was starting the JA Ranch in Palo Duro Canyon, engaged Martinez to accompany him to Las Animas, Colorado, for additional ranch supplies, Martínez assured him that he would kill his outlaw brother-in-law himself if he continued in his crime spree.
In the fall of 1876 two brothers named Casner were traveling through the area with sheep and considerable money, having successfully mined a small fortune in the California gold fields with their father and another brother. L'Archevêque, accompanied by an unsuspecting lad named Ysabel Gurules, tracked down the campsite, and L'Archevêque killed the two brothers. He subsequently killed a Navajo herdsman. Gurules fled and brought word to the pastores at Borrego's plaza. Martinez and several companions lured L'Archevêque to a small adobe house and shot him; he died a few hours later and was buried at a site near the south bank of the Canadian River that subsequently became known as Sierrita de la Cruz.
Through the agency of Goodnight, word of L'Archevêque's murders reached John Casner and his remaining son, John Lewis, who were prospecting around Silver City, New Mexico. The Casners arrived at Goodnight's Home Ranch in the spring of 1877, claimed the sheep, and threatened to kill every Mexican in the Panhandle. They lured Colas Martínez and Felix Gurules away from their house on the pretence of being hunters in need of guides, and shot them. The next day they hanged two more pastores from a chinaberry tree. Because the Casners harassed people in the area for some time several pastores and their families abandoned their plazas and returned to New Mexico. John and Lew Casner settled for a time in Donley County and were listed in the 1880 census as stockmen. On at least one occasion they quarreled with the JA cowboys over ownership of a maverick steer, and apparently they were a thorn in Goodnight's side. However, trouble between the two parties soon subsided, especially after William McDole Lee and other cattlemen bought out the pastores and the Panhandle Stock Association was formed to bring law and order to the region.