In a classic example of shooting the messenger, Creon angrily threatens the sentry who informs him about Polyneices' burial, ordering him to find out who buried the body on pain of death. It's not the sentry's fault that someone buried Polyneices, but as it's already been established, Creon doesn't really go in for fairness all that much. He's a monstrous tyrant who simply must be in control of everyone else at all times. It's simply incomprehensible to him that anyone would have the sheer effrontery to defy his express orders. After all, Creon is king, and what he says goes—or at least, it should so. So his immediate reaction to the news of Polyneices' burial is to assume that one of the sentries has been bribed. In Creon's fevered imagination, that's the only rational explanation for why someone would go against his wishes.