I think that Brandon's last name might be Radzinsky (simply a friend of Minkowsky). Both obviously killed themselves by a shot in the head. Desmond has seen both of their blood-leftovers on the ceiling in the swan station and the wall on the freighter.
Maybe he came to close to the Island, traveled in time like desmond, somehow went down the hatch, survived by pushing the button, went insane and tried to end this nightmare by killing himself. The moment he points a gun to his head down in the swan-station is the moment he points a gun to his head on the boat. He pulls the trigger - he dies twice.