The S&P 500 extended its decline in early afternoon trade, falling 7% to trigger a so-called circuit breaker, resulting in a 15-minute market-wide trading halt for stocks. The S&P 500 was halted at 2,351.79, while the Dow stands at 19,576.75, down 7.8%. The Nasdaq Composite is at 6,872.41, down 6.3%.