One other important nuance about managing PTSD, often one responds to a situation as if they were in the earlier traumatic situation. Maybe not so relevant to veterans (I can’t speak first hand about this), but from an abused child’s perspective… when someone in the present treats them even remotely like their abuser the response can be not to the present but to the past. An unreasonable over-reaction in the present may seem “uncalled for” but was a perfectly important survival skill in the past.
And, before you judge, realize it might not have been the first time they’ve been triggered recently, but the first time the reaction was an uncalled for response. Every situation is a new battle and the best way to help is to simply make the assumption that the “uncalled for response” is not about the present, and the person acting that way just needs a little compassion.