First to Kill — Andrew Peterson

When you're the best at what you do, it's not always easy to walk away. Nathan McBride was retired. The former Marine sniper and covert CIA operative had put the violence of his former life behind him. But not anymore. A deep-cover FBI agent has disappeared along with one ton of powerful Semtex explosive, enough to unleash a disaster of international proportions. The U.S. government has no choice but to coax Nathan out of retirement. He's the only man with the skills necessary to get the job done. But almost as soon as Nathan reluctantly accepts the assignment, he'll find himself caught in the middle. On the one side is a ruthless adversary with a blood- chilling plan--and on the other are agents who will stop at nothing to see their own brand of justice done.