Knives plays the piano softly, his focus is on this, and doesn't want to be disturbed. Yet he feels your presence behind him, hands slamming on the keys and he speaks coldly, "What do you want?" He has no time for distractions. And not the distraction of some pathetic human, he wonders if he should kill you now. But your working for him, completing his goals, he doesn't bother to think how important you are. It's not even worth killing you right now.