Stocks fell broadly on Monday as artificial intelligence fears re-entered Wall Street and added to concerns over President Donald Trump's decision to raise global tariffs following the U.S. Supreme Court's decision last week.

The Dow Jones Industrial Average (DIA  ) plunged over 800 points to end the session at 48,804.06. The broader market S&P 500 Index (SPY  ) also dropped over 1% to close at 6,837.75, while the tech-heavy Nasdaq Composite (QQQ  ) lost more than 1.1% to settle at 22,627.27.

Over the weekend, Trump said he would increase global tariffs to 15% from 10% following the Supreme Court's decision on Friday that ruled against the majority of the president's import duties.

"I, as President of the United States of America, will be, effective immediately, raising the 10% Worldwide Tariff on Countries, many of which have been 'ripping' the U.S. off for decades, without retribution (until I came along!), to the fully allowed, and legally tested, 15% level," Trump wrote in a Truth Social post on Saturday.

"During the next short number of months, the Trump Administration will determine and issue the new and legally permissible Tariffs," he added.

Separately, the European Union asked the White House for clarity in a statement on Saturday on whether or not trade deals made between the United States and Europe could be affected by the new global tariff rate.

"The European Commission requests full clarity on the steps the United States intends to take following the recent Supreme Court ruling on the International Emergency Economic Powers Act (IEEPA)," the Commission wrote. "The current situation is not conducive to delivering 'fair, balanced, and mutually beneficial' transatlantic trade and investment, as agreed to by both sides and spelled out in the E.U.-U.S. Joint Statement of August 2025."

Also moving markets, major cybersecurity stocks such as Zscaler (ZS  ) and CrowdStrike (CRWD  ) fell lower on Monday as growing investor concerns over artificial intelligence disrupting multiple industries spilling into the sector. This added to the drag on software stocks, with IBM (IBM  ) shares dropping over 10% on Monday after rival Anthropic unveiled new programming capabilities for its Claude Code offering, which could be used to modernize legacy systems that run on COBOL -- a key business for IBM.

"Hundreds of billions of lines of COBOL run in production every day, powering critical systems in finance, airlines, and government. Despite that, the number of people who understand it shrinks every year," Anthropic wrote in a blog post on Monday. "AI excels at streamlining the tasks that once made COBOL modernization cost-prohibitive."

"Legacy code modernization stalled for years because understanding legacy code cost more than rewriting it," the blog added. "AI flips that equation."

Looking ahead, market participants will turn their attention towards earnings reports from companies such as Home Depot (HD  ), Keurig Dr. Pepper (KDP  ), and First Solar (FSLR  ) on Tuesday. Other major highlights include economic readings on consumer confidence, housing prices and a series of speeches and remarks from Federal Reserve policymakers throughout the session.