just tell me who's responsible 

I suspect many longs got liquidated and stop loss orders got triggered. There were 7 red candles on the 15 minute chart before the massive dump.
What sort of longs get liquidated from a price that was so close to ATH? That must be some ridculously crazy leveraging
Trailing stop loss makes some sense though.
I guess Bitmex doesn't count. Never mind. I'm just thinking $500 is a big move when at these prices it is less than 10%. Still not getting used to these prices.