The VIX (see the chart below) is showing increasing stress levels.

Note that the VIX has risen above the blue dotted resistance line level. Since the VIX moves opposite to the stock market, this was a bad event on Monday.

However, the big risk for the VIX would be if it went above the (higher) red dotted resistance line. That level is a resistance line that goes back 3 and 1/2 years and would bring a lot of carnage should the VIX move above that level.