Sean was CTU's primary analyst despite being inexperienced and having only worked with simulations. He readily greeted Kim Bauer, who was starting as an intern. CTU was later taken hostage by the terrorist group led by Peter Madsen, and Sean was shot and killed as a demonstration of Madsen's power. As a result of Walker's death, Adam Kaufman was assigned to CTU Los Angeles later that evening to fill his position.
Findings at CTU · Operation Hell Gate · Veto Power · Trojan Horse · Cat's Claw · Vanishing Point · Chaos Theory · Storm Force · Collateral Damage · Trinity · Head Shot · Death Angel · Deadline · Rogue · Trial by Fire