Wild Horse Mesa (movie, 1947)

Dave and Chito are working for Melburn who is looking for wild horses. Olmstead has his men looking for then also. When Dave finds them first, Olmstead buys them from Melburn and then kills him. A clue leads Dave to Olmstead's where he breaks in and finds the murder weapon. When he takes his evidence to the Marshal he learns Olmstead has been murdered and he is the one under arrest.