The Dow Jones closed down over 600 points and over 3 percent Friday, the day the United Kingdom voted to exit the European Union and Prime Minister David Cameron said he would resign by October.
Stocks plunged sharply, US government bonds soared and currencies broke decades-old records after Britain's decision. The Dow Jones industrial average plunged as far as 650 points in late afternoon trading, and a last-minute, 100-point rally was stifled by the closing bell. It closed at 17,401, down 610 points from the open.
The S&P 500 index had its worst open, in percentage terms, in 30 years. It lost 3.6 percent to close at 2,037. The Nasdaq lost 4.12 percent Friday.
The S&P 500 and Dow Jones industrial average erased year-to-date gains and joined the Nasdaq composite in negative territory for 2016, CNBC reported.
According to S&P Down Jones Indices, global markets lost $2.1 trillion Friday — $830 billion of that across U.S. markets.
"The biggest thing is markets are operating and there isn't a liquidity crisis. This isn't a Lehman moment," Chris Gaffney, president, EverBank World Markets, told CNBC.
Trading was earlier described as "orderly," despite the widespread rush to sell. At one point during the middle of the night, pre-market trading suggested a decline of well more than 700 points.
"We're going to have tremendous uncertainty for a period of time," David Gerstenhaber, the president of Argonaut Capital Management, told CNBC. "This is not going to be a rapid exit."
Banking stocks were particularly hard hit, with Citigroup and J.P. Morgan Chase both dropping sharply at market open.
The Brexit result was a stunner, with all indications going into the vote that "remain" was going to edge out a narrow victory. When it became evident that the polls were wrong and that Britain would vote to leave, markets panicked in a way rarely seen before.
The news was so dire that traders estimated up to a 15 percent chance that the Federal Reserve would reverse course and cut interest rates this year to help the economy.
"I hope there's a poll in a month" asking Brexit voters if they regret their choice, Council on Foreign Relations President Richard Haass told CNBC. "Because my guess is there'll be serious voter's remorse."
The value of the British pound against the US dollar fell more than 10 percent to lows not seen in more than 30 years, though it also made back some ground later in the day. For a currency market used to measuring moves in hundredths of a penny, the moves had relatively little historical precedent.
The yield on 10-year US treasury bonds plunged to 1.45 percent before rebounding, as scared investors sought the safe haven of US government debt. As investors buy bonds and their price rise, their yield - or the interest rate that they offer - falls.
Meanwhile the price of another safe haven, gold, rose by about 5 percent. In panic situations like the one seen Friday, investors typically sell indiscriminately in effort to put their capital in the assets, like gold, seen as safest.
The declines in the United States followed European stock markets, which saw some of their sharpest losses in decades. Banking stocks - many of them major U.S. employers too - were especially crushed. Property stocks and retailers were also battered.