Policital Prisoner is a faction quest given by Boris. He asks the player to travel to Tixa Prison in order to shoot Braeburn.
To get there, head to Briar Valley and then talk to Boat Racer to get a boat. Follow the Boat racing course up until point 17. You should see it on the left. Braeburn is standing on the second floor of the prison. You can either infiltrate the prison and kill him or simply snipe him out from any vantage point around the prison.
It is often best to do this quest at the same time as the the Masud Father Figure II quest as Soloman is right nearby.