I've been told that the body can autonomously go into a sort of 'Emergency Survival Mode' wherein part of that mode may involve purging the stomach contents and/or voiding the bladder and/or emptying the bowels.
It is a 'down & dirty' way to offload any processes that might take body resources or otherwise hinder a Total and Complete focus on 'Fight or Flight'.
You can see a similar response sometimes in Marathon/Extreme Endurance runners/athletes.
The look on that mother fuckers face ahahahah lol!