While volume climbed to rank as distribution there wasn't a significant relative loss for markets. However, the selling perhaps marks an indication that the summer lull is a maximum for the Brexit recovery.

Today's selling started yesterday and continued through the day. The S&P shows this with the Inverse Hammer followed by today's red candlestick combo. The support line from the Jobs Data breakout hasn't been breached and this may be enough to keep longs in their positions. However, a weak open tomorrow could open the flood gates, and a loss of 2,160 may see others pile in.

The Nasdaq saw a recent 'sell' trigger and this was compounded by today's distribution selling. Other technicals are healthy, but the index lacks a natural support level for value buyers to step in. The 50-day MA near psychological 5,000 may be the best dip-buyer spot.
 

There was a straight reversal of yesterday's gain for the Russell 2000.  These two-bar reversals can mark tops, but there needs to be follow through with another down day to confirm. Shorts may go aggressive with a stop at 1,245 with position size depending on the entry price relative to risk.
 

What happens tomorrow may largely be determined by the opening half-hour. A gap down and/or sell off during this period may be enough to see such selling last throughout the day.