The S&P 500 sank 1.7% for its worst day in two months. The Dow Jones Industrial Average dropped 748 points, or 1.7%, and the Nasdaq composite tumbled 2.2%.

Mangione, 26, didn't speak at the hearing. Judge Gregory Carro ordered him to remain handcuffed, calling it a security measure. Mangione’s lawyer, Karen Friedman Agnifilo, argued that the sight of ...