Nah, it was one person. Whoever it was wants out. Is this coin premined?
15 BTC is nothing to scoff at, props to the buyer and congrats.
Nah probably someone who either bought at 45 and wants to take a quick 10+% or a bag-holder who bought higher and saw the buy wall as an opportunity to get out.
Was this on Cryptsy? Seems to me that most of the volume there is made up of bots judging by the strange orders. 99% of the orderbook on any coin consists of less than 0.001 of a BTC. Probably a bot just got triggered as the price went up again.