This master's thesis analyzes crisis communication on the social media platform X (Twitter), using the terrorist attack in Christchurch, New Zealand, on March 15, 2019, as a case study. The objective is to investigate, analyze, and describe the communication strategies and tactics employed during and after the selected event. The thesis provides insights into the importance of analyzing crisis communication on social media in contemporary society, highlighting the global impact of the specific case through the example of the X (Twitter) platform, which is frequently used by individuals and institutions to share information and public reactions in crisis situations. The research aims to understand the responses of relevant institutions, organizations, and key individuals to the terrorist attack via X (Twitter), the methods of communication with the media and the public, and the nature of the messages conveyed. The research questions focus on identifying key communication tactics, audience reactions to posts, and the dissemination of information among X - users during the selected crisis event. The emphasis is on a symptomatic investigation that can serve as a basis for identifying best and less effective practices in crisis events, thereby potentially providing a model for planning crisis communication. In this context, the theoretical framework is applied to conduct an analysis of a deliberately chosen sample of posts on the mentioned social media platform, followed by a proposal for a possible crisis communication model on the selected platform in the event of future crisis situations.