Mass casualty incidents generate a sequence of response events from the emergency services, requiring the allocation and use of resources in a timely fashion. In this paper we describe a pervasive system that helps emergency services optimize their efficiency and coordination. The system emulates a multiple casualty emergency response environment in which contextual information, retrieved from victims' wearable or mobile devices, guides early assessments on the health condition of the affected population. Additionally, we analyze the behavior of our system under different conditions and derive the necessary parameters for achieving accurate estimations. Our main contribution is the enhancement of the existing emergency response process for mass casualty incidents through the use of pervasive computing technology.