The person encountering the stress does not have to be the one whose life is threatened. This stress can also occur to witnesses. By it's nature, Post Traumatic Stress is one of the worst types of stress a person can encounter. It is stress of a nature that is threatening to a person's survival. The psychological and physical reactions of our mind and body to Post Traumatic Stress are at the extremes.
Some police officers thrive on stress.
They seek out incidents that most people would not care to encounter in their lifetime. Many people seek out a job in police work for this challenge and the personal rewards it provides. Overcoming stress of great magnitude can provide great personal rewards, but these jobs can and do ruin many lives. For a variety of reasons, some of which are not known, many police officers work through Post Traumatic Stress and its affects. It's lasts more than two days, but no longer than 4 weeks.