Critical incidents often challenge the structures of a community to their upper limits. Therefore not only victims and their relatives, but often the whole community or region have to deal with disaster consequences, which have to be psychologically processed and fostering mental reactions, often far from normal experience. Meanwhile different rescue and security specialists are exposed to high pressure to perform and mental stress. In modern disaster deployments also specialists in psychological early interventions and caregivers are integrated, which are as well not immune to stress. Despite the chaotic initial position in the aftermath of disaster, a great deal of scientific evidence concerning acute stress reactions and possible long-term mental health consequences has been gathered. But chaos also holds hidden, often poorly measurable and therefore scientifically not comparable aspects, which might nevertheless be useful for understanding of and coping with psychological trauma. Therefore this article addresses not just scientific, evidence based medical and psychological aspects of traumatization but focuses especially on less measurable experiences from defined disasters.