Maybe someone pushed the wrong button or he knows something we don't know? What is your theory?
Even if they had insider information, there would be better ways to get out.
I can only see one logical reason to dump in one go - trying to move the price lower.
I would say the fact that whatever happened on btc-e was the inside information. A select few may or may not have traded in front of what was likely a large margin call on the exchange, but the fact that there was a margin call (or something else that caused the price to crash) was the cause of the crash, not the other way around.
