'Brexit' Jitters Weigh on Dow Jones Industrial Average

The Dow Jones Industrial Average (DJIA) fell off sharply after the open -- shedding as much as 130 points -- with healthcare stock Merck & Co., Inc. (NYSE:MRK) leading the path lower. Uncertainty is once again building ahead of next week's "Brexit" referendum, even while campaigns in the U.K. remain suspended. As the U.S. dollar weakens, oil prices are moving higher, with July-dated crude oil last spotted up 2.7% at $47.47 per barrel, but failing to give stocks a boost. As such, the major indexes are all on pace for hefty weekly losses on this quadruple witching Friday.

Continue reading for more on today's market -- and don't miss:

• Why Apple Inc. (NASDAQ:AAPL) could be facing a major hurdle in China -- and the pain it's causing for these 3 stocks.
• The gun stock rewarding a crop of last-minute options bulls.
• Plus ... Checking in on the CBOE Volatility Index (VIX), the SPDR S&P 500 ETF Trust (SPY), and other noteworthy stats at midday.

Smith & Wesson Holding Corp (NASDAQ:SWHC) is among the stocks with unusual options volume at midday. The gun maker is up 7.5% at $23.39 after reporting better-than-expected quarterly earnings, along with an upbeat outlook. SWHC calls are trading at nine times their typical intraday rate -- in the 99th annual percentile. The most active options so far are the June 22 and 23 calls, but it looks like most of the action is coming from traders closing out their positions ahead of tonight's options expiration.

AAPL supplier Synaptics, Incorporated (NASDAQ:SYNA) is among the worst performing stocks on the Nasdaq, shedding 10.6% to $54.05 -- and hitting a new two-year low -- after news the company will eliminate 160 employees and cut pay for some executives was met with a price-target cut at J.P. Morgan Securities. The shares have given up nearly one-third of their value so far in 2016.

Among the top performers on the New York Stock Exchange today is Lumber Liquidators Holdings Inc (NYSE:LL), surging 23.2% to $16.30 on reports the company will stop selling Chinese-made laminate flooring. A controversy regarding the flooring materials led the stock to drop off sharply last year. While the shares haven't yet made much of a recovery -- still off 21% year-over-year -- they may have found a new ally in the form of their 80-day moving average.

   
The CBOE Volatility Index (VIX) is up 0.4 point, or 2%, at 19.75.

Today's put/call volume ratio on the SPDR S&P 500 ETF Trust (SPY) is 0.87, with calls outnumbering puts. SPY was last seen down 1 point, or 0.5%, at $206.24.

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