There may be malingerers who do damage to all but it does not change the fact that psychological trauma happens to people forced to witness terrible things.
It does not have to be a trigger puller either. Someone who normally is away from the tip of the spear who is suddenly confronted with carnage can be as strongly affected.
This is a problem in law enforcement as well as war.
No apology necessary. My friend's brother recently came back from Afghanastan and she says he's very different. Loud noises scare him, he refuses to talk about what he has seen, and his marriage is on the rocks. It's taken a toll on him.