from ZeroHedge:

Crypto exchange BitMEX is currently investigating “unusual activity” involving large sell orders on its BTC-USDT spot market overnight that sparked a flash-crash dragging the price of BTC (in USDT) down below $9,000 (while the price remained above $66,000 on other exchanges)…

Doesn’t seem like a very smart move for the ‘rogue seller’ to dump over 400 BTC at that time of day into an illiquid market – why not wait until the US BTC ETF market is running its magic and sell into that liqudity?