I don't know, but it looked like a bunch of day traders bumping into each other trying to get out at the end of the day. I ended up getting back in about 4 minutes till the ending bell.
That last half hour lost BAC market cap has now been regained in premarket with BAC trading in the 8.60's right now. Nice craziness to the markets. Heart attack city and "buying opportunity", LOL) brought on by the Ultra Shorts.