The protesters occupying Hamilton Hall on the campus of Columbia University seemed ready to stay a while.
They had a microwave, an electric teakettle and sleeping bags, images distributed by the police show. On a blackboard in a classroom turned canteen, next to the words “Free Palestine” in bubble letters, they had written a chart for occupiers to list their dietary restrictions (two were vegan, one vegetarian).
In another classroom, they made a chart for security duties in two-hour shifts, and listed three Maoist revolutionary slogans as inspiration, according to the police videos.
“Political power comes from the barrel of a gun,” one of the slogans said.
For two weeks, Columbia’s campus had been the focal point of a growing crisis on college campuses around the country. Pro-Palestinian demonstrators set up tent encampments, held rallies and otherwise attempted to disrupt academic activities in an attempt to force universities to meet several demands.
But the takeover of Hamilton Hall was a new turning point. The university decided to call in the police to clear the building — drawing both harsh criticism and praise, and raising new questions about who, exactly, was behind the growing unrest.
The people who took over the building were an offshoot of a larger group of demonstrators who had been camping out on campus in an unauthorized pro-Palestinian protest. On Tuesday night, more than 100 of them — people inside the hall along with others outside on campus and those beyond Columbia’s gates — were arrested.
In the days since, Mayor Eric Adams, police officials and university administrators have justified the arrests in part by saying that the students were guided by “outside agitators,” as the mayor put it. “There is a movement to radicalize young people, and I’m not going to wait until it’s done and all of a sudden acknowledge the existence of it,” he said on Monday.
In an interview, Mayor Adams said that 40 percent of people arrested after the protest at Columbia and another that night at the City University of New York “were not from the school and they were outsiders.”
But at Columbia, at least, the percentages appeared to be lower, according to an initial analysis of police data by The New York Times.
Most of those arrested on and around Columbia’s campus appeared to be graduate students, undergraduates or people otherwise affiliated with the school, according to a Police Department list of people who were arrested that night that was obtained by The Times.
At least a few, however, appeared to have no connection to the university, according to The Times’s review of the list. One was a 40-year-old man who had been arrested at anti-government protests around the country, according to a different internal police document. His role in the organization of the protest is still unclear.
The day after New York City police officers stormed into the building through a second-floor window and rooted out the protesters from Hamilton Hall, new details emerged about both the occupation of the building and the operation to reclaim it. The details revealed a 17-hour-long student occupation that was both destructive and damaging to property, amateur, but in some respects, carefully organized.
The Police Department list showed that most of the more than 100 people arrested in the sweep of Hamilton Hall and other parts of campus on Tuesday evening were in their late 20s, white and female. The average age was 27; more than half were women.
The records do not specify which of the people were arrested inside the building. But at least 34 taken into custody on or around the campus were charged with burglary, which is defined by New York law as unlawfully entering a building with intent to commit a crime.
As of Thursday afternoon, at least 14 people who had occupied Hamilton Hall and later been arrested appeared in Manhattan Criminal Court. All of them were charged with trespassing, a misdemeanor.
The occupation began early Tuesday morning, after a group of protesters decided to escalate their efforts to force Columbia to divest from companies supporting Israel.
As hundreds of protesters gathered around Columbia’s central campus, forming a picket, a smaller group of demonstrators carried tents to a lawn on the opposite end of campus from Hamilton Hall, apparently to create a diversion, several witnesses said. At the same time, a second set of protesters approached the building.
A protester who had been hiding in the building after it closed let the others in, according to Columbia officials. Those protesters entered the building and told the security guard there to leave, said Alex Kent, a freelance photographer who entered with them. They then began the process of bringing in supplies and barricading themselves in.
Some of the demonstrators wore Columbia sweatshirts; others wore all black. They also wore gloves, and masks around their faces. They hauled in metal police barricades to help reinforce the doors against entry, according to images shot by Mr. Kent.
Mr. Kent and the police said that the protesters covered security cameras, and threaded heavy metal chains through windows they had smashed in the building’s French-style doors, securing them with bicycle locks. Protesters carried wooden desks and tables from classrooms to help reinforce the doors. They joined the pieces of furniture together with white plastic ties to make them harder to move, police images show. They secured another door with a vending machine.
They got into a shoving match, Mr. Kent said, with a facilities worker who was still in the building, but the worker ultimately left. Outside, a career protest organizer in her 60s, Lisa Fithian — whom Mayor Adams later labeled a “professional agitator”— tried to talk down two student counterprotesters who were blocking the throng from further barricading the entrance. The protesters tried to physically remove the two students, who ultimately walked away; Ms. Fithian was not arrested.
Police officials had been in regular conversations with Columbia for weeks about how to handle the increasingly entrenched student encampment. Now, university officials were in crisis mode.
The school’s leadership team, including the board of trustees, met throughout the night and into the early morning, consulting with security experts and law enforcement, Nemat Shafik, Columbia’s president, wrote in a letter to the community.
“We made the decision, early in the morning, that this was a law enforcement matter, and that the N.Y.P.D. were best positioned to determine and execute an appropriate response,” she wrote.
Once the police got that call sometime after 11 a.m., “We had to put together a plan fast,” according to Jeffrey Maddrey, the chief of department, who described the police response during a news conference the day after the arrests.
On Amsterdam Avenue, outside Hamilton Hall, the police brought in a BearCat truck equipped with an extendable ramp, so that officers could bypass the barricaded front doors and climb into an upper-story window.
Just after 9:30 p.m., a group of officers in riot gear began lining up and then balancing across the BearCat’s platform, one by one. Once inside, the police said, some students started throwing things at them.
Chief Maddrey said the police decided to deploy “distraction devices”— commonly called “flash-bangs” or stun grenades — that produce a very strong noise and burst of light to temporarily disorient people’s senses. At least eight loud bangs were heard echoing on footage from a police body camera.
Another team of officers entered through the building’s front doors, cutting the metal chains and rapidly dismantling the items blocking the entryway, the body camera video showed.
While city officials praised the police for what they said was restraint in clearing the campus, protesters said some officers at the scene had been aggressive with demonstrators.
Protesters posted videos that appeared to show police officers pushing and dragging demonstrators outside of Hamilton Hall’s main entrance during the arrests. The Columbia Spectator reported that outside Hamilton, officers threw protesters to the ground and slammed into them with metal barricades. Most journalists had been required by the police to leave the area and could not document the scene.
“Students were shoved and pushed,” said Cameron Jones, a student in Columbia’s Jewish Voice for Peace chapter, who was watching from a nearby building. One protester lay motionless for several minutes, and was zip-tied while in that position, Mr. Jones said, before she came to and was escorted away by the police.
“It really seems as though the university, the police and Eric Adams are just trying to save face and not acknowledge the police brutality that happened on our campus,” he said.
Mayor Adams said there had been “no injuries or violent clashes” and the Fire Department said no one in Columbia’s immediate vicinity had been transported to the hospital for care.
In addition to the arrests at Columbia, the police arrested over 170 protesters at City College on Tuesday night. Some of those arrested were students who had built an encampment earlier in the week in a plaza on the school’s campus.
But they also included people who had joined a protest outside the campus’s locked gates, on a public sidewalk. Many of the people on the police list were arrested near City College appeared to be unaffiliated with the school.
On the list of protesters arrested at or near Columbia were a handful of people without clear ties to the university, including one man who apparently lives in the neighborhood and who was arrested outside, and a woman who describes herself online as a “poet and farmer” who went to college in Vermont.
Attempts to reach several of the protesters on the list were unsuccessful as of Thursday afternoon.
Columbia students received more news on Wednesday that their semester would not be returning to normal.
While classes had already ended Monday, the school announced that all final exams and academic activities on the Morningside Heights campus would be fully remote for the rest of the semester.
“It is going to take time to heal, but I know we can do that together,” Dr. Shafik wrote.
Liset Cruz, Eliza Fawcett, Eryn Davis, Bing Guan and Alexandra Eaton contributed reporting. Kirsten Noyes contributed research.