The Tokyo Whale did. He keeps dumping at around 10k. If you actually follow the market, you will see there is strong growth, everything is bullish, lots of volume from lots of traders, then WHAM! The whale takes a dump. Lots of volume from a single trader.
I've noticed the price of BTC flash crashing today, and was wondering if the Tokyo Whale had anything to do with it. Thanks for confirming that

At least we know that he'll give the price a chance to recover before dumping again. I guess if you can beat the Tokyo Whale to the next BTC selloff, you'll be doing pretty well.