Ralph Compton's The Hunted

Big for his age, young and impressionable drifter Charlie Chilton is taken in by the gruff leader of a gang of small-time crooks and ne'er do wells who sees something of himself in kindly, wayward Charlie. But Grady Haskell, ambitious ruffian with a shady past, soon joins the gang, convincing Charlie's friends to pursue a big score. Charlie fails to thwart the crime, and the heist turns bloody. As the only gang member caught alive, Big Charlie will soon swing for the crimes. He makes a daring escape, determined to track down Haskell and the gang and prove his innocence. 

Big Charlie Chilton knows better than to lose his temper, but when a loudmouth threatens to expose his long-buried secrets, he can't help but teach the man a lesson about being quiet. Unfortunately it turns out the man was about to make an important supply run for the town's marshal, and Marshal Watt knows just enough about Shotgun Charlie's past to draft him into service in his stead.