Oooh, sounds good! I'll probably do that.
Could be that the other personality doesn't really know the loved one who died, they just started tormenting the poor boy because they "noticed" his guilt(AKA, it started being affected by it; previously, they were just annoying and made the teen forget things) and "capitalized on the opportunity"(I'm putting certain things in air quotes because the schizophrenia can't really think at this point(not being real and all) and can only really repeat things the teen has seen and the teen's personal fears, lol-). Then, when the teen calls them out on it, they don't really have an answer. xD
Then they have an identity crisis because they're supposed to be the teen's personal tormentor for letting their loved one die, and they don't even know the loved one in the first place? And, they're losing control over the boy as well!? THIS WASN'T SUPPOSED TO HAPPEN!