NCIS Season 3 Episode 13

NCIS Sunday leaves are canceled when Lt. Cmdr. Wilkerson, who helped plan the route of a nuclear fuel rods transport train, goes missing just before the nuclear fuel leaves. Wilkerson's cellphone is traced, Wilkerson was locked in the car trunk after it was taken. The team finds out Wilkerson was an over-active volunteer in a private pedophile hunter group, so what was the motive?