Mostly it was a sharp drop in stock prices in China that lead to insecurity and a selling of major European indices and then a major sell off from the American market. A massive snowballing effect that really had more to do with timezones than economic problems. We'll see what happens tomorrow.
The Chinese stock market was up 130 percent over the past year, so a 9 percent drop is not much. Same for the Dow, it is still way above 12,000. I would look at this as a buying opportunity in both countries.