What led to the arrest of Mahmoud Khalil, a prominent pro-Palestine activist at Columbia University? Although he is a United States permanent resident, Khalil is facing deportation. The Trump administration says it's part of a broader effort to combat anti-Semitism, but critics see a chilling attack on political speech, with deportation being used as a weapon to silence dissent. US President Donald Trump says Khalil is the first of many to come. What happens next?