William Wold was a soldier in the US Marines. The following links to a combat video where he is interviewed.
Skip to about 6 mins as before that is dead insurgents. VIDEO is NSFL before that. Only warning.
After that, read this article.
http://www.vice.com/read/killing-up-close-0000001-v20n1
Not intended to be anti-war or pro-war. Just a story to help you understand PTSD and its effects.