IMO it was an intentional act, not a bunch of panicked people.
They did not say who was responsible for the 550 billion.
Was it a government agency that deposited the money over time, then removed it in an hour or two?
Thus a manufactured scenario to force Bush to act, and approve the 750 billion?
The street was warned and ready for the break in Money Market $1/share value. The Lehman paper default was huge news that triggered an industry wide ahhhhh panic.