Our brains are very interesting the way we handle information when we are in our fight or flight mode.
You must have run into witnesses that all saw something different after an event or accident.
I've had training that taught us that we get tunnel vision in an emergency and all our strength is tuned into the crisis we are facing. They keep training on the same information over and over again so we can react from training instead of our flight or fight response. I know your training must have been similar and more intense than mine. I almost got myself into a pickle once due to my reaction with a real crime. I work with client's who have retardation and other mental illnesses. We are taught never to hurt them or be hurt if at all possible. I ran into a guy trying to break into my office and that training kicked in when it shouldn't have. Luckily he was drunk and didn't have a weapon. I started retraining my mind that there were times when it's ok to hurt someone. As a police officer I'm sure you went through both kinds of training. I'm sure that training kicked in when you had to shoot that young man.
The things that we see in life change our reality. We can both be standing in the same place and one person will feel safe and another person will feel threatened. I really try to avoid the news or other things with so much negative information. I don't want to add to my little "what can happen" box. It's already too big.
Hugs,
MG