Routine organizational decision-making is a complex process, but organizations have procedures in place to support decision-making for routine situations. However, when an organization faces a crisis, the standard processes in place may not be enough to react appropriately to the crisis. Sometimes, due to the scale of the crisis and the resources needed, organizations may need to collaborate with other organizations to ensure success. This thesis addresses the design of such a mutual aid system as a type of a decision-making system. Our approach is based on the Operational Procedure Model used in avionics for specifying the dynamic behavior of operationally embedded reactive software-based systems. Using this approach, we designed and tested a mutual aid system to be used by five hospitals in Montgomery County, Maryland. Based on this experience, we propose a revised methodology for designing crisis decision-making systems.