" Yet trauma has been hard for the academic world to define and therefore understand its full scope. Part of the challenge is that ‘bad event’ is subjective. Let’s take an example. Consider, say, a fire at an elementary school. A veteran fire-fighter can walk right up to the flames and put them out, business as usual. In contrast, a first-grader witnessing his classroom burst into flames will experience minutes of intense fear, confusion, and helplessness. This illustrates one of the key issues in understanding a potentially traumatic event. How does the individual experience the event? What is going on inside the person; is the stress response activated in extreme and prolonged ways? "

― Bruce D. Perry , What Happened To You?: Conversations on Trauma, Resilience, and Healing