Check the candles on the markets. 100k BTC sold in one day at one exchange can cause a drop of even 15-18%, but this only if the other markets are also selling.
A smart seller would spread between the top 2-3 exchanges and then the result would be about 3x smaller drop (and better price for the seller).
Depending on market's mood, such a drop can cause a downtrend or it grows back in less than a day. I expect more the second.