So, someone experiences a traumatic event where they are incredibly (read: way beyond the normal every day occurrences) disturbed, frightened, stressed, or pained in an event involving (actual or threatened) serious injury or death to themselves or others. Shock is a variation of Post-Traumatic Stress Disorder.
People in shock typically start out dazed, sometimes semi-conscious, with an inability to comprehend or pay attention to stimuli, and can appear disoriented. They progress to withdrawal or extreme agitation. Anxiety, impaired judgment, confusion, and depression tend to follow. For most folks, these episodes go away after a few days. Many people don't remember the events leading to and through the shock. Those unlucky enough to suffer from PTSD may deal with it for the duration of their lives.
Someone that experiences true shock really needs to get to a counselor, a doctor, a priest... somewhere that they can get treatment and work through the shock in a healthy manner. Statistics show that people that experience shock and shock-like symptoms for longer than 30 days have a much higher risk of PTSD. Medication and counseling can help prevent a lifelong disabling ordeal.