From experience I can say what I felt as it was happening to the best of my memory.
I witnessed a really bad accident and everything that could be done was being done as we all waited for an ambulance. A guy said I should sit down so I did.
As soon as I sat down my mind just started to stop thinking. You know how a really complex machine might have a dozen or more switches and gauges and a specific order to start and stop it ?
It was like someone was performing a shutdown sequence on my mind. All I know is I woke up in the hospital, I remember nothing in between. I don't know if I passed out, or if I was questioned, or anything at all really. So be ready cause it sure can happen and adrenaline is only good for so long.
Short, shallow breaths, dry mouth, a dislocated feeling, that's about all the warning you will get, ohh, and someone suggesting that you sit down.
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