U.S. stocks opened lower on Sept. 14 as a selloff in key artificial-intelligence shares followed warnings from top U.S. executives about safety risks and calls to slow AI development. The S&P 500 fell 0.59% to 7,611.44, while the Nasdaq Composite dropped 1.19% to 26,018.502. The Dow Jones Industrial Average initially rose 0.34% to 52,750.88 but later reversed course and was down 0.26%. Earlier market data had reported broader declines and an 11.81% rise in the VIX, alongside sharp losses in several AI-related stocks.