Mahmoud Khalil, a graduate student at Columbia until this past December, was inside his university-owned apartment Saturday night when several Immigration and Customs Enforcement agents entered and took him into custody, his attorney, Amy Greer, told The Associated Press.

Greer said she spoke by phone with one of the ICE agents during the arrest, who said they were acting on State Department orders to revoke Khalil’s student visa. Informed by the attorney that Khalil was in the United States as a permanent resident with a green card, the agent said they were revoking that instead, according to the lawyer.

A spokesperson for the Department of Homeland Security, Tricia McLaughlin, confirmed Khalil’s arrest in a statement Sunday, describing it as being “in support of President Trump’s executive orders prohibiting anti-Semitism.”

Khalil’s arrest is the first publicly known deportation effort under Trump’s promised crackdown on students who joined protests against the war in Gaza that swept college campuses last spring. The administration has claimed participants forfeited their rights to remain in the country by supporting Hamas.

McLaughlin signaled the arrest was directly connected to Khalil’s role in the protests, alleging he “led activities aligned to Hamas, a designated terrorist organization.”

As ICE agents arrived at Khalil’s Manhattan residence Saturday night, they also threatened to arrest Khalil’s wife, an American citizen who is eight months pregnant, Greer said.

Khalil’s attorney said they were initially informed that he was being held at an immigration detention facility in Elizabeth, New Jersey. But when his wife tried to visit Sunday, she learned he was not there. Greer said she still did not know Khalil’s whereabouts as of Sunday night.

“We have not been able to get any more details about why he is being detained,” Greer told the AP. “This is a clear escalation. The administration is following through on its threats.”

A Columbia University spokesperson said law enforcement agents must produce a warrant before entering university property, but declined to say if the school had received one ahead of Khalil’s arrest. The spokesperson declined to comment on Khalil’s detention.

In a message shared on X Sunday evening, Secretary of State Marco Rubio said the administration “will be revoking the visas and/or green cards of Hamas supporters in America so they can be deported.”

The Department of Homeland Security can initiate deportation proceedings against green card holders for a broad range of alleged criminal activity, including supporting a terror group. But the detention of a legal permanent resident who has not been charged with a crime marked an extraordinary move with an uncertain legal foundation, according to immigration experts.

“This has the appearance of a retaliatory action against someone who expressed an opinion the Trump administration didn’t like,” said Camille Mackler, founder of Immigrant ARC, a coalition of legal service providers in New York.

Khalil, who received his master’s degree from Columbia’s school of international affairs last semester, served as a negotiator for students as they bargained with university officials over an end to the tent encampment erected on campus last spring.

The role made him one of the most visible activists in support of the movement, prompting calls from pro-Israel activists in recent weeks for the Trump administration to begin deportation proceedings against him.

Khalil was also among those under investigation by a new Columbia University office that has brought disciplinary charges against dozens of students for their pro-Palestinian activism, according to records shared with the AP.

The investigations come as the Trump administration has followed through on its threat to cut hundreds of millions of dollars in funding to Columbia because of what the government describes as the Ivy League school’s failure to squelch antisemitism on campus.

The university’s allegations against Khalil focused on his involvement in the Columbia University Apartheid Divest group. He faced sanctions for potentially helping to organize an “unauthorized marching event” in which participants glorified Hamas’ Oct. 7, 2023, attack and playing a “substantial role” in the circulation of social media posts criticizing Zionism, among other acts of alleged discrimination.

“I have around 13 allegations against me, most of them are social media posts that I had nothing to do with,” Khalil told the AP last week.

“They just want to show Congress and right-wing politicians that they’re doing something, regardless of the stakes for students,” he added. “It’s mainly an office to chill pro-Palestine speech.”