President Donald Trump is warning that the arrest and possible deportation of a Palestinian activist who helped lead protests at Columbia University will be the first "of many to come" as his administration cracks down on students protesting the war in Gaza. Mahmoud Khalil was arrested Saturday by Immigration and Customs Enforcement agents. His lawyer says the agents claimed the government was revoking his green card. The Department of Homeland Security has said the arrest was in response to Trump's executive orders prohibiting antisemitism. A protest is scheduled later Monday at ICE offices in Manhattan.