Leaders in high-reliability organizational contexts such as firefighting, emergency medicine, and law enforcement often face the challenge of making sense of environments that are dangerous, highly ambiguous, and rapidly changing. Most leadership research, however, has focused on more stable conditions. This study analyzed 100 reports of “near-miss” situations in which firefighters narrowly escaped injury or death, drawing upon sensemaking and high-reliability organizational theories to provide a grounded theory of leadership processes within extreme events. Themes related to direction setting, knowledge, talk, role acting, role modeling, trust, situational awareness, and agility were key categories. Further abstraction of the data revealed the higher-order categories of framing, heedful interrelating, and adjusting as key characteristics of the overall social process of leadership within dangerous contexts, labeled organizing ambiguity. These findings highlight leadership as a collective sensemaking process in which ambiguity is reduced and resilience promoted in the face of danger via interaction among and between leaders and followers.