Abstract: The larger the scale, scope, and duration of a disaster, the higher is the number of response units. However, with more units involved in the response also the heterogeneity of responder units drastically increases in terms of capabilities, experiences, practices, techniques, tactics, and procedures. As a result, the coordination and overall management of the response becomes an increasingly challenging endeavor. In the response to the 2014 Oso/SR530 landslide disaster in Washington State over one hundred agencies were involved, which presented a huge coordination task for the incident command. This empirical study is exploratory and focuses on the activities and interactions of professional responders, particularly, in the early phases of the response. It amends and complements previous studies on the subject by identifying and describing in detail various challenges in the early response. It also discusses recommendations on how to tackle and potentially mitigate the challenges identified in future responses.