This paper presents results from a field experiment of IT-use in emergency response work of a fire crew. A prototype has been developed to probe for instances of sensemaking supported by IT-use in such work. The findings have been analyzed in relation to research on design of emergency management information systems and sensemaking theory. Key findings from the field experiment suggest that there is a potential conflict between the role-based emergency management information systems and the shared use of information technology of first responders. Further it is advocated that prototypes should be used to explore the extrinsic of the work practice difficult to uncover using only direct-observation or interviews.