I was expecting this drop a bit earlier, around monday since in past weekend the BTC was in overbought with RSI in the range 70-80. Probably the overbought situation mixed to that story of "sleeping billionaire BTC wallet" awakened today after 4 years, the big Silk Road fund selling orders (100k BTC) brought us to this bloodbath. Anyway it's just a matter of time, in my opinion the BTC will climb soon to 8000$, I don't know about the alts, probably they still suffer a bit more.