Fear, panic, and uncertainty. The market will recover. Anyone investing in stocks must be willing and able to ride out the volatility, and stay for the long run. The market will reward you for it.

FWIW, I managed a $500 million portfolio for a national charity for 12 years, including the 2008 crash. There was panic aplenty back then, and those who acted on that panic and left the market not only bought high and sold low, but they missed the recovery.