Desert Guns (1936)

Kirk Allenby is hired by the Cattleman's Association to track down and arrest a rancher who they believe is stealing cattle. Allenby finds his quarry but is astounded to discover that that man, Bob Enright, looks enough like him to be his twin. He is forced to shoot Enright, but as the man lay dying he gets Allenby to promise that he will help Enright's sister, who is being forced to marry the real boss of the cattle rustling operation, who has framed Enright in order to take over his ranch.