Hunting by Moonlight. The Ilyirzi Scions, #1

Kelly Townsend has a big problem. Someone has killed two men, both of them omegas. Worse, no one in the townships know who they were. When a councilman's son becomes the third victim, the sheriff finds the politcal heat turned up. To his surprise, the Council inform him that he has a new partner on the case, one of the vampire-like aliens whose world their colony was allowed to be established upon.  Pilar of House R'jil'yae'k is honored to find himself assigned to the case.
The humans are notoriously insular, allowing only minimal trade conducted from afar, making the opportinity unique. He knows he will face resistance to his presence, both due to his species being known as vampires thanks to the resemblance to human ancient legend, and also because he's an omega himself. Still, as the first omega Hunter of his House, he's determined to not only track his prey and bring him to justice, but to do his people proud. As secrets old and new are uncovered, the political landscape becomes even more fraught.
Both of their people's futures hang in the balance as truths are uncovered that change everything they know. For Kelly and Pilar, the case turns out to be only the beginning.