In this thesis work, I examine the use and adoption of online communication media by 840 fire and police departments that were affected by the 2012 Hurricane Sandy. I began by exploring how and why these fire and police departments used (or did not use) online media to communicate with the public during Hurricane Sandy. Results show that fire and police departments used online media during Hurricane Sandy to give timely and relevant information to the public about things such as evacuations, damages, weather, and cleanup and to engage in two-way communications with their constituents. In their messages, fire and police departments sought to make the information provided more credible by referencing, rebroadcasting, and recommending other authoritative entities. Though some departments saw online media as a useful and effective means of communication with members of the public, other departments found them difficult to use given the challenging circumstances of Hurricane Sandy such as flooding and power outages. Next, I explore how a large-scale disaster event like Hurricane Sandy affects online media adoption by affected fire and police departments. I found an increase in online activity over Facebook, Twitter, and Nixle by the affected fire and police departments compared to before Hurricane Sandy. However, it is unclear whether this increase in online activity can be attributed to Hurricane Sandy or a natural increase over time.