Sean Mason was the FBI San Francisco District Director during Day 2, 3, and 4. He died when he caused an explosion to distract Benjamin Tredaku's army during the White House raid so Rick Jackson could save President Joseph Wald.
Sean Mason arrived at the end of Day 2, to supervise Chris Andrews in order to bring down President Jackson Hicks' terrorist workings. Sean acted very rude, and constantly had something to say about Chris' judgement. Sean later warmed up to the employees of FBI San Francisco.
During Day 3, Sean was at FBI San Francisco to supervise the interception of the cordilla virus. He called in Rick Jackson to help find the virus. During the day, Sean proved to help out and work well with the employees. He also became friends with the employees.
Day 4EditAt the start of Day 4, Rick Jackson, Arnold Robinson, and Sean Mason were temporarly transferred to FBI DC to help stop a suspected attack conducted by General Benjamin Tredaku. When Sean and Rick went to go work out of the White House, Rick incapacitated Sean so Sean couldn't stop him from giving Michael Harris a private interrogation. Sean later woke up, and was transporting Rick to the White House jail, when he got a call from Ralph Wilson saying that Benjamin Tredaku was about to raid the White House. Sean took the President's transponder (Tredaku was tracking President Wald using the transponder) and diverted Tredaku's men to Sean. Sean was then taken hostage.
Later, Rick and President Wald were taken hostage, and Sean told Rick that he overheard Tredaku talking to an unknown conspirator, and that this attack wasn't over. Sean then told Rick to find out who Tredaku was working with, and ran into one of Tredaku's men. He then stole the pistol from the soldier, and blew up some C4 that was in the White House Panic Room. Sean died so Rick could save President Wald.