There's one big reason why the final 10 minutes of trading could get ugly today

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Near 2:00 pm ET, the Dow was down about 380 points, the S&P 500 was down 46 points, and the Nasdaq was down 98 points.

The major indexes were off their lows, but still down 2% in a bad start to September, which is traditionally the weakest month of the year for the stock market.

In an afternoon email Rich Barry, a floor governor at the New York Stock Exchange, said that one big thing could make the final 10 minutes of trade even uglier: buybacks.

Barry noted that word on the Floor is that corporations buying back stock are a big buyer today.

And if this is indeed the case, the final 10 minutes of trading could be ugly because corporate buyback orders have to be canceled at 3:50 pm ET; the closing bell rings at 4:00 pm ET.

And so if the big supporter of stocks - which, all things considered, isn't doing much for the market given the big sell-off - steps away with 10 minutes to go, a complete lack of buyers could see bids tumble into the close.

In his note, Barry also highlighted 3 stats making the rounds on Tuesday:

1. Currently, 99% of the S&P 500 is trading in the red.
2. In August, after being hit by one of the most volatile trading periods since the financial crisis, $5.7 trillion was erased from the value of stocks worldwide.
3. From Barry's "trader contacts": "We have heard unconfirmed chatter of a large beginning-of-the-month pension rebalancing making the rounds: with Energy and High Beta names for sale with proceeds rotating into Defensive names." Barry added that it, "seems like people are backing into that theory given the price action, but it is worth noting."

Less than 2 hours to go.