Same thing that happened on August 2014.
Market maker or other any other major player dumps a big quantity of coins that wipes out an important portion of the whole orderbook which causes a margin cascade of longs closing. Considering that BTC-E being illiquid, this is highly profitable if he has shorts opened that he will soon close/already closed or longs/coins orders at around $150.
Being a shady as hell exchange I wouldn't be surprised if somebody from BTC-E is somewhat responsible himself, having insider info on where all the stops are placed and margin calls would be triggered.
Stop hunts and shenanigans happen in forex everyday, can't see how a shitty anon exchange for magic internet money would be any different.
This, or an Agora drug dealer or admin dumping because he wanted to buy a boat or something.
Still, the results (margin cascade) are the same.

The btc-e order book is so thin it wouldn't take that many coins to create a giant crash. On bigger exchanges with more liquidity it would take millions of dollars of coins to dump down to the same price. The only time it recently happened on the big exchanges was in the new year. Btc-e is not big enough to create a significant knock on effect on other exchanges.