The Fallen Man by Tony Hillerman

Sprawled on a ledge under the peak of Ship Rock mountain for eleven years lies an unknown body, now only bones. At Cabyon de Chelly, three hundred miles across the Navajo reservation, a sniper shoots an old canyon guide who has always walked that pollen path in peace. At his home in Window Rock, Joe Leaphorn, newly retired from the Navajo Tribal Police, connects skeleton and sniper, and remembers an old puzzle he could never solve. At his office in Shiprock, Acting Lieutenant Jim Chee is too busy to take much interest in the case - until it hits too close to home. Bringing the beauty and mystery of the Southwest to vivid life once again, Tony Hillerman has reunited Joe Leaphorn and Jim Chee in an evocative mystery in which the past and the present join forces in a most unholy union.