Super Colt 38

Billy Hayes, the marshal, discovers that the bandit whom he has been pursuing so long, and who has for months been torching his county, is none other than an old friend from childhood. Upon being confronted with the truth, the friend draws his gun, and Billy is forced to kill him in justifiable defense. Overwhelmed by guilt, he renounces his office and swears to never use arms again. He rides off toward the town where he and his old friend grew up together. (imdb)