Noticed big and fast moves on my (tick) screen abt that time. We have 7 trading days before default which..surprise...surprise ...happens on day SPX Oct options expire. Expect pretty sharp moves and put buying on moves up. I rolled out my short calls/puts Oct to Jan and imagine a lot of traders are using the volatility to do same.
This thing is being sold relentlessly despite the market makers attempts to turn the delta for VWAP into the long bond auction.
Based on the comments here I thought it was absolute carnage in the markets, but it's barely down 1% at this point, right?