The Teacher. The Fast Gun Series, #6

He buried his gun. but not his name. Macon Farrell was only sixteen when a bloody range war along the Nueces Strip turned him into the Rio Kid-a lightning-fast gunfighter with a reputation he never wanted. Years later, after the Civil War, he's ready to put away his six-shooter for good. In the Wyoming Territory, he joins a group of settlers looking for a second chance, and intends to become a rancher and school teacher.
But after a ruthless cattle baron decides the settlers' land belongs to him, hired guns ride into town, and the only man fast enough to stand against them is the one Macon tried to leave behind. Soon, he must decide whether he's the peaceful teacher building a future, or the Rio Kid who knows some wars can only be won at the draw. A western adventure set on the American frontier, THE TEACHER is the sixth book in the Fast Gun series by Terence Newnes.