In a show of solidarity, hundreds of protesters gathered at Foley Square on Monday to protest the arrest of Columbia University graduate Mahmoud Khalil.

The green card-holding Palestinian activist, who helped lead protests at the university last year, was detained by immigration authorities Saturday and is now in an immigration jail in Louisiana.

“It’s absurd, it’s outrageous. It’s a clear abuse of power directly coming from the White House,” Layan Fuleihan, education director of People’s Forum, said.

Fuleihan is also a Columbia graduate.

She says the arrest of Khalil is a move by President Donald Trump to intimidate protesters.

“It’s an authoritarian move. If in any other country in the world this was happening, the U.S. would say this is not democracy. Well, it’s happening right here and we need to make sure everyone realizes what’s going on,” Fuleihan said.

Trump says Khalil’s arrest is “the first arrest of many to come.”

“This is his test case to see how the public responds and that’s why people are very upset,” protester Bruce Trigg said.

“I knew this thing would start to happen, and when it actually does start to happen, it’s horrifying,” protester Jocelyn James said.

Many at the rally wondered what Mayor Eric Adams had to say about the arrest.

At a public safety event earlier in the day, Adams evaded the question.

As protesters took to the streets, faculty gathered outside Columbia University to also stand with Khalil.

“His only offense was executing his constitutional rights to free speech and peaceful assembly,” Michael Thaddeus, vice president of Columbia University American Association of University Professors, said.

In a campus-wide letter, Columbia says it did not call ICE on the student and will follow the law, meaning law enforcement must have judicial warrants to enter non-public university areas.

“Our message to Washington is that we are not silenced, we are not afraid and we stand together determined this ongoing assault on our fundamental rights,” Thaddeus said.

Meanwhile, 1.6 million people have signed a petition to demand his release.