I’m guessing he killed her because he knew she wasn’t from this world. Or for some rea...

I’m guessing he killed her because he knew she wasn’t from this world. Or for some reason to save her and him. He prob found out he could leave with her but only if he killed her and himself or sum. Him being obsessive and stabbing himself is either he’s crazy or he was only allowed to leave if he hurt her in some sort of way so mentally and physically (killing her) I dunno tho ┑(￣Д ￣)┍