Sweden until recently has been spared from major terrorist attacks. Research, however indicates that mass casualty incidents caused by terrorism are increasing in the western world and are expected to continue to increase within the near future. The execution of the emergency response plan and local emergency protocols is ultimately dependent on leadership at the service and unit level. As a result of the terrorist attack in Stockholm on April, 7^th 2017 the medical organisation in Stockholm county were put on the highest alert. The emergency department [ED] charge nurses working during this specific event became key players in implementing and organizing the disaster response at the emergency departments.

There is a lack of research highlighting the charge nurses´ experiences of leadership during disaster response at EDs following major incidents caused by terrorism.

The aim of the study was to describe the charge nurses´ experiences of managing the initial response to the major incident at emergency departments in Stockholm on April, 7^th 2017.

Participants were selected using criterion sampling. All eight EDs in the Stockholm region were invited to participate, of which five accepted. At these five EDs were seven charge nurses working during the major incident and thus available for inclusion. Semi-structured interviews were conducted. Data were analysed using qualitative content analysis.

The results of the analysis yielded to two categories, first the perceived experiences of security consisting of the subcategories, work according to the local emergency response plan, experience and knowledge and controlled information. The second category was the perceived experiences of uncertainty consisting of the subcategories, unclear leadership, disturbances and deviation from the local emergency response plan, lack of knowledge, lack of information and uncontrolled information.

The conclusion from the result was that the charge nurses was in a central position in the response following the event, and that the management of the initial response was successful. In some cases, a need for clarification of the chain of command, extended training and effective crisis communication was identified, which could optimize the disaster management.