Way of the Hatchet. Book One of The Hatchets Trilogy (en Inglés) - Michaeli Knight;Edge O. Erin

The discovery of a severed arm and a fish-hooked foot has Officer Ethan Birchom focused on finding a killer. It's a change of pace from playing with his dog, searching for missing persons, and grieving a long-deceased daughter.
Now, Ethan is dodging bullets - well, mostly - navigating a new relationship, and resurrecting Cold Cases. Strangely, he's seldom felt so alive. Maybe happiness and solving cases are in his future?
Unfortunately, with love building and danger closing in, Ethan unearths something that is as archaic as it is modern, as ageless as it is mortal, and as wicked as it is incorruptible. In his attempt to stop more good from dying young, Ethan is in over his head.