Sutton sent Martin Kail to find and bring in Susan Walker, a former operative of CTU Washington who had gone rogue, killing DOD agent Donald Frick. After Kail himself was caught by Susan, she explained what was happening: someone inside CTU was trying to collect a package of money for themselves. They realised that it must be Sutton as he was the only one with the relevant access codes and so set off to bring him to justice.
However, they were fatally wrong, not realising that it was, in fact, the analyst Kelly who was the mole. She shot and killed Sutton before Martin or Susan could do anything about it.