Trader Brian Jones on Twitter: "S&P down 5% in last 3 days. Brutal drop. Watch 2950. That's the key support and will tell us if things will get worse for the market than we thought." / Twitter

S&P down 5% in last 3 days. Brutal drop. Watch 2950. That's the key support and will tell us if things will get worse for the market than we thought.