Assuming there is not an organic cause, Dementia, low blood sugar, a brain issue, they are scared and insecure and trying to keep control of everything in their life. The cause or causes of this could be anything and might be recent or buried in the past. Look at their life, the people around them, work and what is going on in general rather than this particular incident.
Even looking closely at their life you may not find the cause because it is inside of them or coming from their perceptions which may be different than what you see. Depending on the relationship you have to this person and their feelings and emotional state, you can always ask them if there is a problem you can help with. Sometimes just knowing that someone else is aware of a problem will let them unload it on you.
You have to decide if you are willing and able to be there for them. It usually isn't easy or pretty.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.