The US State Department's number two on Thursday threatened to strip visas over online support for the killing of right-wing influencer Charlie Kirk, encouraging internet users to flag foreigners' posts. "In light of yesterday's horrific assassination of a leading political figure, I want to underscore that foreigners who glorify violence and hatred are not welcome visitors to our country," Deputy Secretary of State Christopher Landau wrote on X. Meanwhile, US President Donald Trump and other officials paid tribute to slain right-wing activist Charlie Kirk on Thursday as the country marked the 24th anniversary of the September 11 attacks. The US president announced that he would soon posthumously award Kirk the Presidential Medal of Freedom -- the country's highest civilian honor. The FBI released videos and images of the suspect and announced a $100,000 award. Trump said, Kirk's the suspect involved in the shooting incident was in custody, adding "someone very close had turned him in."