Following the tragedy at Sandy Hook School, there has been a great deal of discussion surrounding PTSD. Post traumatic stress disorder is a mental health condition that is triggered by a terrifying event. It can make it virtually impossible form some people to cope with their post trauma lives. It's essential to get treatment as soon as possible after PTSD symptoms appear.
The MAYO Clinic has a comprehensive fact sheet about PTSD. Generally they fall intor three categories:
Intrusive memories - flashbacks, dreams
Emotional numbing and avoidance - avoiding talking about the event
Anxiety and increased emotional arousal - sleep disorders, destructive behaviour
You should seek medical care if you find yourself fixating on disturbing thoughts or feelings for more than a month, or if you can't get your life on track. If you are thinking about harming yourself or someone else then you should call 911 or seek immediate help from friends, loved ones, or other emergency responders.