Methodic (2007)

Methodic tells the story of a boy who becomes demonically possessed by an ominous presence known as "The Dollman". Forced to obey his dark half, the boy ultimately murders his parents on his birthday and is sentenced to a life under a microscope at the state mental hospital. But evil cannot be contained so easily. Instead, "The Dollman" simply bides his time, dwelling within the boy- waiting for the day when he will become powerful enough to completely take over his human host. And when that day comes, god help us all.