Black Rock Guardian by Jenna Kernan

Ty Redhorse plays both sides of the law. Now he's caught between his ties to the tribe's gang and his cop brother – and the FBI wants him to choose. Complicating the stakes is Beth Hoosay, the stunning FBI agent who always follows the rules...except when it comes to their sizzling attraction. But how long can Ty play this dangerous game before he gets caught in the crossfire?