The Pinkerton agents caught a break in December 1900, when Cassidy posed alongside Longabaugh, Logan, Carver, and Ben Kilpatrick in Fort Worth, Texas, for the now-famous "Fort Worth Five" photograph. The Pinkerton Agency obtained a copy of the photograph and began using it for wanted posters throughout the West.

With the authorities closing in, Cassidy and Longabaugh fled to New York City, and from there departed to Buenos Aires aboard the British steamer Herminius on February 20, 1901, along with Longabaugh's companion Etta Place. Cassidy posed as James Ryan, Place's fictitious brother.

On November 4, 1908, near the town of Tupiza in southern Bolivia, two men thought to be Cassidy and the Sundance Kid robbed a payroll. Three days later the supposed bandits were surrounded by Bolivian soldiers in San Vicente, and a shootout ensued. During a lull in the fighting, soldiers heard a man screaming inside the house, then two successive shots were fired. The next morning, authorities entered the house and found two bodies with numerous bullet wounds to the arms and legs. Judging from the positions of the bodies, local police believed that Cassidy had probably shot the fatally wounded Longabaugh to put him out of his misery, then killed himself with his final bullet.

Paul Newman's portrayal of Butch Cassidy earned him a Best Actor nomination at the British Academy Film Awards, but he was beat out for the award by his co-star, Robert Redford, who portrayed the Sundance Kid.