Rubio’s letter notified DHS that he had revoked both targets’ visas, setting in motion plans for U.S. Immigration and Customs Enforcement to arrest and attempt to deport them, according to a senior DHS official and another U.S. official who spoke on condition of anonymity to describe how the operation against Khalil took shape.

Nearly 100 people were arrested after protesters gathered at Trump Tower in Manhattan Thursday to denounce the arrest of Mahmoud Khalil, a Palestinian activist detained by ICE over his involvement with pro-Palestinian demonstrations at Columbia University.