Recent terrorist attacks have increased the need to examine the public’s response to such threats. This study focuses on the content of Twitter messages related to the 2016 terrorist attack on the Berlin Christmas market. We complement the collective sense-making perspective with the terror management theory (TMT) perspective to understand why people used Twitter in the aftermath of the attack. We use structural topic modeling to analyze our dataset of 51,000 tweets. Our results indicate that people used Twitter to make sense of the events and as part of typical reactions in TMT, that is, to validate their own worldviews and maintain their self-esteem. In accordance with TMT, we found that people used Twitter to search for meaning and value, show sympathy for victims and their families, or call for tolerance, but also to express nationalistic sentiment and greater hostility toward values and views other than their own. We further show that topics varied over the course of the attack and in the days that followed. Whereas in the first two days there were many emotion-related tweets and operational updates, subsequent days saw more opinion-related tweets. Our findings contribute to the literature on collective behavior in the aftermath of terrorist attacks.