General economic news has been good for the last year or so, if not longer, which lead investors to go on a buying spree. It's very possible this created a small market bubble that is now correcting. This potential correction is however negatively reinforced by Chinese economic indicators, which are seriously down. China has devalued its currency multiple times lately, and this along with their cooling economy have ripple effects across the world for multiple reasons, chiefly them being the second-largest economy of the world, but also in particular for their prevalence in supplying manufacturing but also being a market for commodities.
While the economic news is not great, it's not the end of the world. Still, it has caused strong Twitter reactions, and some are even trying to capitalize on the fear and prey on people's emotions. Pat Robertson specifically blamed the bad economic news as God's punishment for American supporting abortion rights.