Seeing one of the co-conspirators greet Hippias in a friendly manner on the assigned day, the two thought themselves betrayed and rushed into action, ruining the carefully laid plans. They managed to kill Hipparchus, stabbing him to death as he was organizing the Panathenaean processions at the foot of the Acropolis. Herodotus expresses surprise at this event, asserting that Hipparchus had received a clear warning concerning his fate in a dream. Harmodius was killed on the spot by spearmen of Hipparchus' guards, while Aristogeiton was arrested shortly thereafter. Upon being told of the event, Hippias, feigning calm, ordered the marching Greeks to lay down their ceremonial weapons and to gather at an indicated spot. All those with concealed weapons or under suspicion were arrested, gaining Hippias a respite from the uprising.