It was during the height of campus demonstrations last spring that Mahmoud Khalil became the public face of student antiwar protests at Columbia University.

Protesters had erected tents on campuses nationwide and demanded colleges divest from financial support for Israel. Police clashed with protesters and arrested hundreds. Columbia quickly became the center of protests against the Israel-Gaza war that swept across the country.

Khalil, a graduate student at Columbia’s School of International and Public Affairs, emerged as an intermediary between student protesters and the school administration.

“Mahmoud has always been a calm, levelheaded person,” his wife, Noor Abdalla, told The Washington Post. “That’s why they choose him as a negotiator.”

Khalil spoke to the press on camera, unmasked — unlike most other protesters whose faces were obscured by masks or tightly wrapped kaffiyehs. He was careful about participating in the increasingly chaotic protests, his friends said, because he was in the country on a student visa at the time.

Several protesters described Khalil as a steady, calming presence; as someone who cracked jokes to take the edge off of stressful situations. He loved the atmosphere in the tent encampment, where people would participate in religious rituals, read, listen to music and dance the dabke, a traditional Palestinian dance. “The encampment was a really beautiful space,” he told The Post shortly after it was taken down by university officials.

But to some Jewish students, the constant presence of the protesters in the center of the school’s Morningside campus — with some of them explicitly excluding Jewish supporters of Israel and chanting things such as “globalize the intifada” — was frightening and exhausting. Parents, alumni, some major donors to Columbia and members of Congress repeatedly called on the school to shut down disruptive protests.

To the U.S. government Khalil, who holds a green card and is married to an American, is a national security threat. Last week, Immigration and Customs Enforcement officers arrested him in an effort to deport him for his involvement in the campus protests.

Secretary of State Marco Rubio said it was necessary to revoke Khalil’s green card because Khalil was allegedly endangering U.S. national security by supporting terrorist groups. President Donald Trump called Khalil a “Radical Foreign Pro-Hamas Student” and said in a social media post that the arrest was the “first of many” for those “who have engaged in pro-terrorist, anti-Semitic, anti-American activity.”

Khalil’s friends and family rejected the government’s accusations, describing him in interviews with The Post as a hardworking, well-respected graduate student and soon-to-be father who was ripped from his family for his courage in speaking out. They told stories of times when he had comforted them, cooking Palestinian dishes such as maqluba, and shared video of him dancing joyfully, holding a small child on his shoulders.

Some in Columbia’s Jewish community feel differently. The day after his arrest, the Columbia Jewish Alumni Association wrote on social media that it was “exactly what needs to happen to restore order to campuses like @Columbia and our country.”

There is no question that Khalil’s activism, without a face covering, made him an easier target for the government.

Protesters wearing masks could be more aggressive, said a close friend of Khalil’s, who spoke on the condition of anonymity for fear of retaliation. “Mahmoud was the complete opposite,” the friend said. “He was always showing his face because he knows he’s not doing anything wrong.”

Khalil’s detention has sparked debates over freedom of speech and protests — dozens of Jewish demonstrators were arrested Thursday at Trump Tower in New York while demanding his release. Some student protesters said they now fear harsh retaliation as the school and federal government move to punish them.

On Friday, the Department of Homeland Security announced that a Columbia student protester had voluntarily left the country after her visa was revoked. It also said that a Palestinian student from the West Bank was arrested for allegedly overstaying a student visa and taking part in protests on campus.

On Thursday, Columbia announced that protesters involved in seizing a university building last year — a group that Khalil had negotiated on behalf of — had been punished with penalties including expulsions, suspensions and the temporary revocation of degrees.

The same day, three federal agencies outlined specific steps the school must take to try to continue to receive federal funding — the first of which was punishing protesters.

Khalil’s lawyer filed a lawsuit Thursday, alongside other students, against Columbia to try to prevent the school from sharing information about him with a congressional committee.

Khalil was born and raised in a refugee camp in Syria and has Palestinian heritage, he said in a clip released Wednesday from a forthcoming film, “The Encampments,” about the 2024 campus protests. A native of the region with deep roots there, his grandmother told him of sharing farmland with Jewish neighbors in Tiberias, now a city in northern Israel, before the 1948 Arab-Israeli war. When the family learned of a nearby village being burned, Khalil said, some of the men went to fight while his grandmother, who was pregnant, left their home and walked 40 miles to Syria. She gave birth along the way.

He said his father was born in a tent in the refugee camp and lived in it until the 1970s, when more solid structures were built.

“To us, it was always a temporary home,” Khalil said in the video, “until we go back to Palestine.”

With the help of a scholarship, Khalil went to college in Lebanon. He went on to work for several years for the British government in international development, including in Lebanon, and worked for a scholarship program.

He met his wife, a U.S. citizen from the Midwest, while they were both volunteering in Lebanon. They moved to the United States in January 2023 so Khalil could begin his studies at Columbia and married that fall, his wife said. Khalil interned at the Permanent Observer Mission of Palestine to the United Nations, she said.

Then Oct. 7, 2023, happened, and he was drawn to the activism simmering on campus.

Months later, in April, protesters broke into and seized Hamilton Hall at Columbia, a university building with a long history of student demonstrations.

Khalil was one of two students nominated by the main protest group, Columbia University Apartheid Divest (CUAD), to negotiate with the administration.

“He’s very diplomatic,” said Tejasri Vijayakumar, who was Columbia College student body president last year. He had a different approach to the protests than many, she said. It wasn’t just that he didn’t wear a mask and was careful about the rules, “he was really willing to have a dialogue.”

Asked whether she thought he supported Hamas or other militant groups, she was one of several students who laughed out loud at the question. “Are you kidding? No. He’s just a sweet guy.”

Some Jewish students, though, said he should have been expelled months ago. “He’s one of the ringleaders” of Columbia University Apartheid Divest, said David Lederer, a junior at Columbia who said the atmosphere on campus has been hostile to Jewish students. “His activism has been pretty viciously militant.”

On Oct. 7, 2024, the first anniversary of the Hamas-led attack on Israel, masked protesters converged on campus. Columbia University Apartheid Divest changed its rhetoric. CUAD announced its celebration of the al-Aqsa Flood, using the name Hamas has given for the Oct. 7, 2023, attack, and praised the leadership of Hamas, Hezbollah and Ansarallah, groups the United States has designated as terrorist organizations.

Later that month, a new group, the Columbia Palestine Solidarity Coalition, wrote an op-ed in a campus newspaper, the Columbia Spectator, saying, “We wish to disaffiliate from CUAD and create a Palestinian-led coalition for divestment from Zionist occupation and apartheid.”

In a recent interview with The Post, Khalil said he was not affiliated with CUAD.

Khalil’s status in the country changed in November when he got his green card, making him a permanent resident, according to court documents.

He was required to undergo security and background checks to enter the United States as a student and later to obtain legal permanent residency, said Amy Greer, a lawyer in his federal lawsuit. “He’s been vetted by our own country and found to be admissible,” she said in a phone interview this week. “He’s a humanitarian. He’s a human rights advocate. He’s a volunteer.”

After earning permanent residency, Khalil continued to object to the war in Gaza.

In January, Trump announced he would track down and deport foreign students who joined in what he called “pro-jihadist” protests.

“It sets a dangerous precedent,” Khalil told The Post at the time, “where peaceful protest is met with severe consequences, eroding democratic principles and academic freedom.

“Columbia University must take a stand,” he said, “protecting international students and their right to speak out without fear of retaliation or deportation.”

Many people on and off campus welcomed Trump’s promise, posting on social media the names of pro-Palestinian students who they said should be investigated, expelled or deported. Khalil was named. One group claimed to have sent a legal memorandum to DHS about him.

Khalil was seen at a protest earlier this month at Barnard College, an independent but affiliated school, that ended with arrests. Some students, hoping to raise awareness about the threat they were feeling, posted on social media photos of fliers that they said were distributed at the event. One depicted a portrait of a Hamas leader. Another carried the insignia “Hamas Media Office.”

“They’re saying that Mahmoud is part of Hamas, which is pretty crazy,” said Layla, a Palestinian student at Columbia who is friends with Khalil. “He’s very kind, very gentle.” He is not antisemitic, she said. “Mahmoud has repeatedly emphasized that he stands against all forms of hatred, all forms of discrimination.”

Following the Barnard event, a Columbia professor and prominent Israel advocate began posting about Khalil, his wife told The Post. She described a frenzy of tweets that started to raise their anxiety about what might come next.

“He would refresh his phone and just watch them come in,” said Abdalla.

Eventually, Khalil decided he needed help. Last Friday, Abdalla said that her husband sent an email to Columbia saying he feared for his safety and asked for help.

On Saturday night, the couple was returning home from a Ramadan dinner when plainclothes officers stopped him at his university apartment. By 3:30 a.m., he was in an ICE detention center in New Jersey. Within hours, he was shipped to another detention center in Louisiana.

The Anti-Defamation League expressed approval. “We firmly believe there should be swift and severe consequences for those who provide material support to foreign terrorist organizations, incite violence in support of terrorist activities, or conceal their identities in order to harass and intimidate Jewish individuals and institutions with impunity,” the organization wrote on X.

Trump, too, celebrated the arrest and said it was just the beginning. “I think we ought to get them all out of the country,” he said. “They’re troublemakers, they’re agitators.”

Within days of his arrest, an online fundraiser brought in more than $400,000 for Khalil’s defense. More than 3 million people have written letters of support, according to an online petition.

“He has access to a TV at the detention center,” said Abdalla, who has been able to receive calls from her husband since his arrest. She said his spirits are intact. “He can see all of the support.”

Razzan Nakhlawi, Aaron Schaffer, Dan Diamond, Isaac Arnsdorf and Maria Sacchetti contributed to this report.