Horn was suspected in the sniper-style murders of rustlers and settlers suspected of cattle stealing throughout the Chugwater River country of Wyoming from 1895 through 1899, when he apparently moved south to the Brown’s Hole region of extreme northern Colorado, an area he knew well from hunting outlaws during his Pinkerton Agency days. Mysterious, sniper-style killings of several cattle rustlers in that area (including Matt Rash and Isam Dart), were attributed to Horn, though never proven. Sometime in early 1901, ill with malaria from his recent volunteer service in the Rough Riders during the Spanish-American War, Horn returned to the Chugwater and recovered at the ranch of his old friend, cattle baron John C. Coble. Horn also picked up his chosen profession of cleaning out rustlers and suspicious nesters by killing and terrorizing them with the constant threat of a bullet from nowhere. Those bullets were almost certainly delivered from his Winchester Model 1894
