Five months after issuing an unqualified audit opinion and an unqualified opinion on internal controls for the audit of the year ended December 31, 2013, for a large publicly traded client, the client and the auditor become aware of a material misstatement in sales revenue for the year in question, which was the result of a material weakness in internal controls. Is this a subsequent event or a subsequent discovery of facts? What are the auditor's responsibilities related to the audit opinion and the opinion on internal controls?