"The magnitude of death and destruction in disasters and the extent of the response demand special attention. Physical safety and security of victims and relief workers must take first priority. After safety is assured, other interventions such as debriefing may begin. Debriefing is a popular, early intervention following disasters in which small groups of people involved in the disaster, such as rescue workers, meet in a single lengthy session to share individual feelings and experiences. The effectiveness of debriefing in preventing later mental health problems is much in debate. As a minimum the following should be considered if you include debriefing as part of an intervention plan."
Center for the Study of Traumatic Stress: http://www.centerforthestudyoftraumaticstress.org