De La Tour was contractually obligated to pay Hochster as his tour guide, and he stated he would not do so. Since we are assuming that the refusal to pay is a material breach, De La Tour made a repudiating statement on May 11.
For an example of a repudiating action, assume that, on May 11, De La Tour turned himself into the police for murder and was immediately incarcerated without bail. De La Tour would have performed a voluntary act (turning himself in) that meant that would not perform his contractual obligation on June 1.