Um. (I always start a message with that!) Okay so this guy has turned into a murderer, and he doesn't want to keep secrets from his girl, so he ends up telling her. And he's worried about if she'll still love him or not after he tells her.
I'm guessing she is pissed! And she doesn't want to be near him anymore, so he kills her, too. "My heart is dead and so are you."
And yes, Atreyu kicks a*!