The First Commandment - Brad Thor

The First Commandment is the sixth novel in the Scot Harvath series. You know you're going against the grain when the president wants you stopped -- dead or alive.

At the end of Takedown Scot's friend Tracy was shot by an assassin's bullet, right on Scot's doorstep. Now Scot is determined to find the terrorist; a terrorist from Scot's past who continues to attack those close to Scot. The president has other ideas. He orders Scott to stand down. When Scot refuses, the president gives the order do whatever it takes to stop Scot. Now Scot has to watch for terrorists and his own special ops buddies. They're all determined to stop Scot. Very highly recommended.