This study relies on information theory, social presence, and source credibility to uncover what best helps people grasp the urgency of an emergency. We surveyed a random sample of 1,318 organizational members who received multiple notifications about a large-scale emergency. We found that people who received 3 redundant messages coming through at least 1 synchronous communication source--for example, phone or face-to-face communication--perceived the urgency of the situation the most quickly, whereas those receiving official messages through asynchronous channels--most often text message--had the lowest sense of urgency. Our findings suggest that by understanding people's reactions to various kinds of redundant communication, organizations can design more strategic emergency messages that capture attention. (Contains 3 tables and 1 figure.)