NEW YORK (AP) — 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.

Despite a stern warning ahead of time, a crescendo of boos could once again be heard Wednesday as Columbia University acting President Claire Shipman acknowledged the absence of their graduate student and pro-Palestinian activist Mahmoud Khalil during her commencement address.