Stock market is crashing
Interest rates have remained extremely low since 2008 even through the economic upturn over the past few years. This has caused an increased amount of borrowing which has caused many to become highly leveraged.
There is speculation that interest rates will be increased soon, which will cause some highly leveraged businesses to become over-leveraged and to default on their debts. The speculation is therefore that we are in for a big correction soon, so investors are trying to take their gains now.