If you had a near death brush with a gunman how would you believe it would affect you?

You are at your kid’s practice, a board meeting, working the line at the factory or in class, just another day then someone produce a gun and starts shooting, maybe hitting people and killing some. How does that brush with death change you? If you were in the building or area but not actually shot at or shot does the trauma of it fade quicker or affect you less? Do you think it would last longer if you were shot at, shot, or a friend or coworker was shot and/or killed? The thoughts and feeling would logically be different than escaping a horrible car crash, almost drowning, etc, but how do you think it would be different?