Black Ops Sniper

This is a story about Victor, a sniper living in the UK who is part of a black ops outfit dubbed only as the unit."  He is on a mission for his life as the sister of one of his former targets tracks him all across Europe. It's the first of a four book series about a shadow unit that operates completely independently, without any government or parliamentary oversight. Victor, a former British Army Sniper, is recruited into the "unit" due to his exceptional marksmanship skills. He recalls one of his earliest targets, a Russian Nationalist. Victor becomes hunted by the target's sister, the best female marksman in Russia, who also kills his best friend. A joint task force is created between the unit and Mossad in order to go after the sniper. Will Victor succeed? Or, has his luck finally run out?