The Power of the Daleks
Bragen was the head of security for the human colony on Vulcan and covertly the chief of the rebel group fighting against the governor, Hensell.
After finding about an incoming inspection from Earth, Bragen donned a enviroment suit and mask, personally shooting and murdering the Examiner summoned to Vulcan. However, in a brief scuffle with the newly-regenerated Second Doctor, his enviroment suit lost a button that later proved him to be the Examiner’s killer.
Bragen then framed Quinn for rebel activity, hoping to be made the deputy governor himself to put himself in a position of genuine power to overthrow Hensell.
Shortly after the capulse’s opening, Bragen planned to use the Daleks to back him in seizing control of the colony, unaware that the Daleks were secretly planning to conquer it themselves.
Once he had a Dalek exterminate Hensell, Bragen dictorially assumed command of the colony and began purging other rebels to secure his posistion. When the Daleks turned on the rebels after giving them support, Bragen tried desperately to regain control but failed.
After the Daleks were destroyed by the Second Doctor, he was on the verge of murdering Quinn when Valmar entered and fatally shot Bragen, killing him. (The Power of the Daleks)