The Columbia graduate student was supposed to attend this graduation celebration. Instead Khalil is in immigration detention, caught up in Trump’s crackdown on foreign students.

The head of Columbia University gave a commencement speech Wednesday acknowledging the absence of student activist Mahmoud Khalil, who was due to receive his diploma this week but is instead in a Louisiana jail facing deportation for his role in pro-Palestinian campus protests.

The chants were in reference to Mahmoud Khalil, a Columbia University graduate student who was detained in March by U.S. Immigration and Customs Enforcement.