President Donald Trump’s “Liberation Day” tariffs plunged the stock market into the red Thursday, marking its worst day since the COVID-19 pandemic began in 2020.

The Dow Jones Industrial Average fell nearly 4%, the Nasdaq Composite about 6%, and the S&P 500 around 5%. These were the Dow and Nasdaq’s worst marks since June and March 2020, respectively.

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The S&P 500 hasn’t been this low since before Trump was elected president last November.

The president announced sweeping “reciprocal tariffs” Wednesday on nearly 200 countries, shocking many global trade partners.

WHAT TO KNOW ABOUT TRUMP’S ‘LIBERATION DAY’ TARIFFS: HOW THEY WORK AND WHO THEY HIT

As the stock market reacted, U.S. companies were hit particularly hard, including tech giants Amazon and Apple, which each saw their stocks drop around 9%. Nike watched its stock drop 14%, while Gap saw a large 20% loss. Common sellers of imported goods, such as Five Below and Dollar Tree, fell 28% and 13%, respectively.

An investment expert said this was the “worst-case scenario” for a tariff reaction.

“This was the worst-case scenario for tariffs, and [they] were not priced into the markets, which is why we are seeing such a risk-off reaction,” Mary Ann Bartels, chief investment strategist at Sanctuary Wealth, told CNBC. ”The big question is if 5,500 can hold on to the S&P 500. If it cannot hold, we may see another 5-10% downside, which could likely point to a bottom of 5,200-5,400.”

Trump said earlier Thursday that the markets were going to “boom.”

“The stock is going to boom. The country is going to boom. And the rest of the world wants to see if there is any way they can make a deal,” Trump said.

Before the stock market opened Thursday, the president said the tariff plan was like operating on a patient.

“The operation is over! The patient lived and is healing,” he said. “The prognosis is that the patient will be far stronger, bigger, better, and more resilient than ever before.”

Not every stock plunged with the news. Companies such as Kroger, Coca-Cola, Pepsi, and Dollar General saw positive gains.

WHICH ITEMS WOULD BE AFFECTED BY TRUMP’S PROPOSED TARIFFS ON CANADA AND MEXICO

However, most investors are now fearful of a recession.

“The impact on inflation will be substantial,” JP Morgan analysts said. “We view the full implementation of these policies as a substantial macroeconomic shock. We thus emphasize that these policies, if sustained, would likely push the U.S. and global economy into recession this year.”