Brennan

Brennan was one of the mercenary task force leaders working for Christopher Henderson during Day 5 assigned to kill Wayne Palmer to prevent him from reaching his contact at Hidden Valley, Evelyn Martin.

Day 5

Brennan and his four subordinates were sent by Christopher Henderson to assassinate Wayne Palmer as he was traveling to the Presidential retreat, to prevent him from contacting his contact in the White House Evelyn Martin. Brennan was foiled when Palmer, a former Marine, knocked out and stole the weapon from one of his men, Cobb, and was driven away from danger by Secret Service agent Aaron Pierce.

After he reported his failure, Brennan was later ordered by Henderson, who was with Evelyn Martin's daughter Amy, to arrive at 4615 Tarpin Street with his men. There, he set up a sniper's perch and was soon ordered to kill Evelyn as she attempted to retrieve her only daughter Amy (who had been kidnapped by Henderson).

Brennan is slain by Jack Bauer

Before Brennan was able to complete his mission, Jack Bauer slit his throat and, with the help of Wayne Palmer, used Brennan's rifle to bring down several of Henderson's other mercenaries and save the Martins from harm.