Anton Modin was an agent with the DSO.
That acronym stands for the Department of Special Operations (DSO), said to be the most secret department in Swedish Military Intelligence. "Everyone employed by the DSO had false identities. ... The DSO adhered to its own set of rules, often far outside the traditional legal system. They reported to an entity known as the National Security Council, which in turn reported directly to the Prime Minister and the Minister of Defense. Only a handful of people knew about these secret laws and reporting structures. The DSO was very much the fourth branch of government and had a tremendous amount of influence on all levels of administration, maybe even more than the political parties."
Modin has been an agent with them for some time, hired shortly after returning to Sweden after graduating from Ohio State University and then fulfilling his "mandatory military service at the Coastal Ranger Academy". The DSO saw tremendous potential in the young man and gave him considerable training in a wide variety of fields. Not only was he trained in as a special forces operative already, he was taught spy craft and then made an expert diver by the nation's Navy and a pilot by its Air Force. Talking with some from those days, Modin was a maverick doing outrageous stunts because he could. Or he was a rogue operative completely off the rails. All depending on the recounter's attitude towards the man.
That was all back then. Back before he met the woman of his dreams and they started a family and soon he had a son he loved and a daughter who he adored. And Back long before they were onboard a ferry that was the target of a horrific action and he barely survived because he was on deck and they were in their cabin when the explosion happened.
Now nearly a decade later, Modin is a drunk. When we first encounter Modin, he "was sweating profusely and had a splitting headache, not to mention a severe case of anxiety". On the wall of his home "hung a portrait of a well built, athletic man in uniform and a green beret; obviously a far cry from the downtrodden human remains before him now".
Modin has given up and is just waiting to die, really. Until something happens that lets him know it was not a terrible accident that took his family but the act of persons unknown and Modin is given a whole new purpose in life - vengeance.