This expression is expression of utmost fear not a brevity or mental resilience.
The fist thing didn't happen right away to be called brevity either.
First he "ducks down" then multiple big dudes jump on top of him providing protection with their bodies and stay there until the situation is under control, security is ensured and he calms down while thinking how he can use this situation to his advantage. Hence the "publicity stunt" fist thing.
It wasn't supposed to be a publicity stunt though.
Hardly anybody will go by the evidence, which very obviously points to this being a lone gunman who bought an AR15, climbed up a roof, and took a bunch of shots at Trump before the Secret Service shot him...
The part of the evidence you forgot to mention is the secret service that failed to do its job which was to put someone on top of the only elevated position there was.
So the only question here is whether this was incompetence or intentional. We know US Secret Service is not an incompetent organization and what I said is standard procedure (to place someone up there, even someone from the Sheriff's department).
Another reason why this was not incompetence is because multiple people saw the armed guy move to the building carrying a weapon, climbing up there and they reported it and they easily ignored it...
