Anthropogenic disasters may be defined as any disaster caused by human action or inaction. Natural disasters occur without human interference. Injuries caused by terrorists and related criminal activities may be broadly grouped into 3 categories: blunt, blast, and penetrating trauma. Most terrorist and criminal activities that create a mass-casualty situation are performed using the weapons most readily available, such as firearms or explosives. A consistent pattern, comparing terrorism with interpersonal violence, is the greater severity of impact on the victim.