Someone close to me had a traumatic childhood, followed by combat duty in the war. He doesn't need to be locked up in the 'funny farm' but I can pretty much guarantee that if two people were hunting him down and chasing him around with a gun, things wouldn't end well. He does fine going about his daily business and even in stressful situations but being chased on the road with a gun would push him over the edge, as it may well do with people without a history of abuse and trauma.
Hmm you make a valid and interesting point. I could very well see this being used as part of his defense.