Reflexive Action — D.R. Evans

Five years ago, one of the wealthiest businessmen in America was assassinated by a professional sniper who was never caught. Now, the dead man's brother has finally tracked down his brother's killer. The assassin, a man known only as Kelton, has retired and is happily married, living on the outskirts of London, his past buried and forgotten.

But when a bomb explosion kills Kelton's wife and maims his daughter, the past comes flooding back, and now it is Kelton's turn to seek revenge -- with the help of the British government's super-secret intelligence agency, GCHQ, and its American counterpart, the NSA.