“Relax dude, or someone is going to think your fucking hurt.”
Welcome to war, bad guys will try to kill you. A recording of US Marines taking cover from an indirect fire (mortar) within their deployment barracks on the FOB. This may quite possibly be what the onset of PTSD sounds like, or simply the sound of an FNG shitting himself.
PTSD is not the result of the total amount of fear and stress experienced, but the individuals feeling of helplessness in the midst of the fear and/or stress.
This video is how most uniformed service members react to indirect fire.