Wall Street took a beating for the second time in three seasons as health crisis jitters and interest rate worries spooked investors.
Tuesday's sell-off put the finishing touches on what was a down month for the Dow and the S&P 500.
Looking at Tuesday's closing action:
The Dow slumped 652 points. The S&P 500 lost 88. The Nasdaq fell 245.
Wall Street followed the weak tone set in Europe after the head of drugmaker Moderna told the Financial Times that existing COVID-19 vaccines would be less effective against the new Omicron variant.
But the selling really picked up after Federal Reserve Chairman Jerome Powell told the Senate banking committee it was time for the Federal Reserve to pull back some of its support for the economy.
"We now look at an economy that's very strong and inflationary pressures that are high and that means it's appropriate, I think, for us to discuss at our next meeting, which is in a couple of weeks whether it will be appropriate to wrap up our purchases a few months earlier."
The Fed had been buying $120 billion in bonds each month to help prop up the economy.
Powell also said it was time to retire the word transitory when referring to the current inflation surge.
Greg Hahn, chief investment officer at Winthrop Capital Management, said Powell's testimony was a needed change in tone, even if it caught the markets off guard.
"The Fed has to remove its bond purchase program before they can move interest rates higher. That's our view of how they'll unwind, start to unwind the stimulative monetary policy. So getting the bond, the bond purchase program out of the way quicker is going to set a path for the Fed to start to move interest rates higher, potentially by June of next year."
The thought of a less-accommodative Fed just as investors face the uncertainty of a new COVID-19 variant was too much for Wall Street to take at the same time.
Oil prices dropped sharply. Crude oil fell 4-1/2 percent to less than $67 a barrel - to lows not seen since August.