Fed doesn't control the market.
Individual exchanges have policies that control when they get shut down, but there was no reason to intervene here.
There was a brief spike downward that is generally caused by automated trading, then the curbs in software (and in the people) correct that and the market tickets back up.
Excluding that, there was a dip at the beginning of the day on anticipation of bad bailout news (failout '08!), which could be entirely expected, and another one during the failed vote, also expected.
Looking like a -500/-600 day, which isn't unreasonable.