Wearing riot helmets and carrying zip ties, Boston police officers moved in one day this week and surrounded a group of pro-Palestinian protesters on a grassy patch of Northeastern University’s campus. Six police wagons were idling nearby, and an officer had issued a terse warning. Mass arrests looked imminent.

Then, without explanation, the riot police packed up and left.

The sudden end to the standoff produced cheers from the protesters, and confusion for those who had been bracing for chaos. In recent days, police officers have rushed in to break up student encampments at the University of Southern California, Emerson College in Boston and Ohio State University. At Emory University in Atlanta, officers used pepper balls and wrestled protesters to the ground, ultimately arresting 28 people.

On quads and lawns from coast to coast, colleges are grappling with a groundswell of student activism over Israel’s ongoing military campaign in Gaza. Administrators are having to make controversial decisions over whether to call in the police, and are often criticized regardless of the route they take.

“They don’t seem to have a clear strategy,” said Jennie Stephens, a professor at Northeastern who attended the protest there to support the students. “I think there’s this inclination to kind of control what’s happening on campus, but then that’s balanced with the optics — or the violence, or the real harm — done to students or faculty or staff or others if there are arrests.”

At Northeastern, where about 100 protesters had linked arms in a circle around a half-dozen tents on a lawn known as the Centennial Common, it was unclear exactly who was directing the police response.