The Lycaeon Legacy by Eugene C. McLean Jr.

Paul McDonough thought he knew what the definition of evil was. As a Navy SEAL and covert operative, he had encountered it on every mission. It was the human seeking wealth and power who murders and tortures their way to the top of the socio-political heap. He would never have considered a supernatural, predatory beast that only looks upon humans as either minion or meal. The arrival of his niece, after the brutal murder of her parents, brings him face to muzzle with these other possibilities.