Marshal of Heldorado (1950)

The Tulliver brothers are terrorizing the town of Heldorado, and Shamrock has been sent to round them up. Arriving posing as a dude, he gets two of them early when they shoot each other trying to shoot him. After he finishes off a third brother, the Tullivers bring in reinforcements and rob the bank. With his identity now revealed, Shamrock organizes a posse and they all head out after them.