President Donald Trump on Thursday sent the stock market plunging downward after he announced new tariffs on Chinese goods over Twitter.

In a Thursday afternoon tweet, the president slammed China for not living up to its promises to buy more American agriculture goods, and he said the United States would soon retaliate by putting "a small additional Tariff of 10% on the remaining 300 Billion Dollars of goods and products coming from China into our Country."

In addition to attacking China for not buying American products, the president also said China had failed to stop the flow of fentanyl into the United States as it vowed to do earlier this year.

"Many Americans continue to die!" the president wrote.

The Dow Jones Industrial Average immediately dropped after the president's tweet, as the stock index lost 200 points in the span of five minutes. Although the Dow had started Thursday up roughly 250 points, Trump's tweet almost immediately erased all gains, as shown by the chart below.

Despite all this, Trump said he was optimistic about upcoming trade discussions with the Chinese government.