Dead Zero by Stephen Hunter

Bob Lee Swagger is called upon by his government yet again. They say they fear there is a renegade sniper out to kill a very important person, at this time unknown, and want Bob Lee to scope out the possibilities for his anticipated attack; ultimately to capture or kill the sniper. Bob Lee says "ok" and begins his research. The more he finds out, the more he is inclined to sympathize with sniper Ray Cruz. Determined to get to the root of the problem, Swagger finds himself switching back and forth, understanding both sides, trying to sort out the truth. Hunter throws in a big surprise for Swagger fans. Read this exciting episode, you will go "oh my gosh, too." Great.