During an operation on Roxara's moon where a squad of marines encountered a zerg changeling, the sqaud's sergeant Walden Briggs found it imperative that SEC know of the situation. Later, when a contingent from the Dominion Marine Corps arrived, Briggs expressed surprise that they were not part of SEC.
Waugh, James. "Changeling." (November 18, 2009). Blizzard Entertainment. Changeling: A Short Story by James Waugh Accessed 2009-11-18.