It should be noted that in the span of 15 minutes, the Dow went from -300 to nearly -1000 to down -500. There's someone on CNBC who's on a trading floor said when it hit -1000, everything went BUY.
UPDATE: Reports are coming in that the massive messup was caused by human error. Typed B (billion) instead of M (million) in a sell order...caused those massive triggers and the massive swing. Currently at -262 on the Dow and rallying VERY fast.