 LaGuerta uses the circumstances of Travis Marshall's death and the fact that she found his blood slide to conclude that Dexter is the Bay Harbor Butcher.Professor James Gellar is a former religious studies teacher at the University of Tallahassee, erroneously fired for stealing an ancient Roman sword which belonged to John the Revelator.Gellar had since then gone underground and was unheard of until the Doomsday Killings.