While the role of mutual beliefs in coordination and collaboration has been extensively acknowledged, the cognitive processes supporting their establishment are left unexplained or simply assumed. Notions like “public event” or “public announcement” usually refer to events or speech acts that create such mutual information states. The goal of this paper is to provide a formal model of the conditions under which mutual beliefs can be established. Agents should be able to perceive and reason about each other epistemic activities in a shared world. To express such reasoning a simple version of propositional dynamic logic with converse operator (CPDL) is adopted.