Books like Occum's Razor: A DS Jason Smith Detective Series

A football player is shot dead in front of a packed crowd of people. DS Jason Smith is put in charge of the investigation. The murder weapon is found in a house across the road from the football ground. It is a rare Russian army issue sniper rifle. As the investigation hits dead end after dead end, two government agents arrive and take over, pushing Smith and his colleagues to the side. As more people die Smith quickly realises these agents are not who they claim to be. He is forced into the dark world of these phantoms and he finds himself at the mercy of his old nemesis; the man who kidnapped his sister years earlier.