Tom Horn is hanged in Wyoming for the murder of Willie Nickell

On November 20, 1903, the infamous hired killer Tom Horn is hanged for having allegedly murdered Willie Nickell, the 14-year-old son of a southern Wyoming sheep rancher.

Some historians have since questioned whether Horn really killed the boy, pointing out that the jury convicted him solely on the basis of a drunken confession that Horn supposedly made to a detective. The jury also seems to have failed to give adequate weight to the testimony of a number of credible witnesses who claimed Horn could not possibly have committed the crime. Yet even Horn’s defenders in the Nickell case do not dispute that he was a brutal hired killer who was unquestionably responsible for many other deaths.

Born in 1860 in Memphis, Missouri, Horn reportedly showed an aptitude for hunting and marksmanship at an early age. After moving westward in the mid-1870s, Horn was at various times a cowboy, miner, army scout, deputy sheriff, and packer for the Rough Riders in Cuba, but his most notorious career was as a hired gun. Horn first worked for the famous Pinkerton Detective Agency which hired him to track down and apprehend—violently if necessary—western outlaws who were preying on Pinkerton clients, like banks and railroads that could afford to pay for private law enforcement where the public system failed them.

But after four years as a Pinkerton, Horn had become bored; and in 1894 he signed on as a hired killer with the privately run Wyoming Cattlemen’s Association. For several years the big Wyoming cattlemen had been fighting a vigilante war in Johnson County against a diverse group of small farmers, sheep ranchers, and rustlers who were resisting their domination. By 1894, negative publicity had made a public war too costly. Instead, the ranchers shifted to more stealthy means, hiring Horn to use his gun-handling skills to deadly effect by ambushing and murdering any man the ranchers marked as a troublemaker. Since he often shot from as much as 200 yards away, most of Horn’s victims never even knew what hit them.

Some historians suggest that Horn may have murdered Willie Nickell by accident, having mistaken the boy for his father. Others, though, argue that it is more likely that Horn was deliberately convicted for a crime he did not commit by Wyoming citizens seeing an opportunity to take revenge.