As Carlos Pero encouraged his mule to lumber up a rugged trail high in the Andes Mountains on the morning of November 4, 1908, little did the courier for the Aramayo, Francke and Cia mining company realize that his every move was being watched. Pero later recounted that after cresting a hill, he was “surprised by two Yankees, whose faces were covered with bandanas and whose rifles were cocked and ready to fire.” The pair of masked bandits robbed the courier of the company’s payroll and then disappeared into the cacti-dotted desolation of southern Bolivia.

The landscape of San Vicente, Bolivia. (Credit: Tyler Bridges/Getty Images)

Three days later, a quartet of Bolivian authorities cornered a pair of Americans suspected of being the perpetrators in a rented house in the dusty village of San Vicente. The Pinkerton Detective Agency—which had been on the trail of Butch Cassidy and Harry Longabaugh, known as the “Sundance Kid,” for years—had warned banks across South America to be on the lookout for the duo who had fled there from the United States in 1901, and later accounts reported those were the identities of the two Americans holed up in San Vicente.

As a Bolivian soldier approached the hideout, the Americans shot him dead. A brief exchange of gunfire ensued. After it subsided, San Vicente mayor Cleto Bellot reported hearing “three screams of desperation” followed by a single gunshot, then another, from inside the house. When the Bolivian authorities cautiously entered the hideout the following morning, they found the bodies of the two foreigners.

The man thought to be the Sundance Kid was slumped against a wall with bullet wounds to his body and a gunshot to his forehead. The man believed to be Cassidy was next to him on the floor with a bullet hole to his temple. Contrary to the 1969 film “Butch Cassidy and the Sundance Kid” in which the outlaws go down in a blaze of glory amid a hail of bullets, it appeared that Cassidy had shot his wounded partner between the eyes before turning the gun on himself.

At an inquest, Pero identified the corpses as those of the thieves who had ambushed him—although all he had ever seen of the masked men were their eyes. But neither Pero nor anyone else ever positively identified the two dead men as Butch Cassidy and the Sundance Kid before their reported burial in an unmarked grave in a San Vicente cemetery. Although descriptions of the deceased bandits bore some resemblance to the legendary robbers, no photographs of the bodies were ever taken to provide proof.

With no conclusive evidence to confirm the deaths of Butch Cassidy and the Sundance Kid, rumors took root that the pair had once again eluded the long arm of the law, and sightings of the duo in South America, Mexico and the United States continued for decades to come.

Family members fueled the stories by insisting that the men had never been killed and instead returned to the United States to live into old age. Cassidy’s sister, Lula Parker Betenson, wrote in her 1975 book “Butch Cassidy, My Brother” that the outlaw had returned to the family ranch in Circleville, Utah, in 1925 to visit his ailing father and attend a family wedding. According to Betenson, Cassidy told the family that a friend of his had planted the story that one of the men killed in Bolivia was him so that he would no longer be pursued. She claimed that Cassidy lived in the state of Washington under an alias until his death in 1937. Betenson said her brother was buried in an unmarked grave in a location that was kept a family secret.

The Sundance Kid and Etta Place, shortly before the pair left for South America.

For decades, husband-and-wife researchers Daniel Buck and Anne Meadows mined South American archives and police reports seeking to track down the true story of what happened to Butch Cassidy and the Sundance Kid, a saga that Meadows detailed in her book “Digging up Butch and Sundance.” While the paper trail pointed to their demise in Bolivia, conclusive evidence as to the identities of the bandits killed in San Vicente in November 1908 rested under the ground of the village’s cemetery.

The researchers enlisted the help of Clyde Snow, the renowned forensic anthropologist who had conclusively identified the remains of Nazi war criminal Josef Mengele, and received permission from Bolivian authorities to exhume the robbers’ bodies. Guided to their purported grave by an elderly villager whose father had reportedly witnessed the shootout, diggers in 1991 unearthed a skeleton of one man along with a piece of a skull from another.

After a detailed forensic analysis and a comparison of DNA to the relatives of Cassidy and Longabaugh, Snow found there was no match. The skeleton was instead likely to have been that of a German miner named Gustav Zimmer who had worked in the area. It’s possible that the bodies of the iconic desperados remain buried elsewhere in the San Vicente cemetery or even outside of its walls. Without any conclusive proof of the whereabouts of the bodies of Butch Cassidy and the Sundance Kid, however, their ultimate fate remains a mystery.