Night Feeders - The Colton Fen Series, #0.5

There's a bad sheriff in town. It's a dangerous existence living out in the Old West, but it's even worse for supernatural entities. When a brothel of concerned vampires reaches out to the Agency for the Betterment of Supernatural Creatures for help, werewolf detective Colton Fen steps in to solve a disappearance. Sheriff Ritters keeps a ghastly group of monsters underground to keep the impoverished people of Clarkville in line.
Anyone foolish enough to cross his path is thrown to the creatures. Even werewolf detective Colton Fen might be out-matched by this vicious murderer.