Survivors and first responders may suffer from psychological trauma in times of terror. In the first moments after a terror attack, fire, police and Emergency Medical Services (EMS) personnel are exposed to horrific scenes which are only familiar to military personnel with combat related experiences. According to the European Association of Fire & Rescue Psychology (AEPSP), between 8–10% of fire and EMS personnel suffer from Post-Traumatic Stress Disorder (PTSD). The prevalence rates of probable PTSD may range from 1.3% to 22.0% in situations of man-made mass violence. In this chapter, the experiences of survivors and first responders, during the terror attacks on Brussels (2016 March 22nd), will be used to introduce the concept of Advanced Psychological Support by the ResQ Squirrel method. This method has been developed in analogy with Advanced Trauma Life Support (which aims to prevent early death of survivable victims by providing advanced medical support) and aims to prevent early development of psychological trauma. The terror attacks on Brussels confronted first responders and psychosocial caregivers with a series of new challenges which have not been fully documented in scientific research till today: the need for acute psychophysiological stabilization during and immediately after (multisite) terror attacks, in a context of horror and gruesome images, the common skills deviation issues (i.e. some first aid techniques are only used by military personnel in wartime deployment), operating in a multidisciplinary context with experienced military personnel, etc. This chapter will list the predictors and determinants for the early development of chronic trauma, based on trauma exposure, dissociative responses, negative emotions, etc. in order to draw a set of practice-based interventions for acute trauma support which are used in daily practice by fire and rescue services personnel in Belgium and France. These interventions may provide the feeling of usefulness and perceived self-efficacy which appear to hamper the development of posttraumatic symptomatology in first responders involved in technological and man-made disaster.