Sean

Sean was one of the CTU Los Angeles field agents working under Director of Field Operations Ronnie Lobell during Day 4.

Day 4
Sean and Aaron were present when Ronnie met Jack Bauer for the first time, and then accompanied Ronnie to follow a lead on the Turkish terrorist Tomas Sherek. Sherek was suspected to be hiding in a Turkish-owned laundry store, operated by Maurice Landstrass. Ronnie sent Aaron and Sean to cover the exits of the store, and the three apprehended Sherek when he revealed himself and tried to flee. Ronnie, Aaron, and Sean returned to CTU and handed over Sherek for interrogation.