Stocks move in tandem with the index.

The Dow 5 days weekly Chart.(5 days to index/options futures expiry.)

The 7th day before the index expiry, the market makers created a bull trap and subsequently hammered it down completing the previous day big crash(X6/5/10) candlestick body.The person or authorities involved have also intelligently chosen the middle of month (the Pivot)--Battle of Midway.

So who says it is technical glitch or some golden fingers that causes the error?They'll be investigating.Don't count on it.They'll be using market traders short- memory to sweep it under the red carpet.

This particular stock(Citigroup) peaks on the 26th April 2010 when it started announcing its first quarterly results.Thereafter begins to slide and never look back.
The U.S. government owns 27 percent of the bank's shares, a stake it acquired when it gave Citi $45 billion in bailout money in 2008 and 2009. Citi has paid back $20 billion in preferred shares, but another $25 billion was converted to common stock last year.The Treasury on even date announced that it is selling its 27% stake.So they must have given a hand for the shorties and market makers to further executed the crash(X6/5/10).

Citi's candlestick chart shows that those manipulators have completed their shorting right up to the crash day lower shadow.Great job indeed.