Devil's gulch western

"John Holt is a traveling gunslinger. He's been liberating dirty towns west of the Mississippi of murdering outlaw trash ever since the Civil War ended. No questions asked. Payment on demand. The only way out of this town is in a pinewood box. Holt's latest job is in Devil's Gulch in Colorado Territory. But wiping out bands of bank robbers is just the beginning. More disorder is brewing, and the skittish mayor has handpicked Holt as the new sheriff....