President Donald Trump was reported uninjured and other top leaders of the United States were evacuated from an annual dinner of White House correspondents on Saturday night after an unspecified threat. There did not immediately appear to be any injuries, and one law enforcement official said a shooter opened fire.

The Secret Service and other authorities swarmed the banquet hall at the Washington Hilton as guests ducked under tables by the hundreds. “Out of the way, sir!” someone yelled. Others...