Since immigration-enforcement agents began their descent on Chicago, acting with seemingly unprecedented speed and ferocity, Evelyn Vargas and her colleagues at Organized Communities Against Deportation have been in a frenzy. They help run an emergency hotline that refers people who have been detained to immigration lawyers and directs their families to support services such as food pantries, emergency housing, and mental-health care. (On a single day last week, it took 800 calls.) And they oversee a team of 35 “rapid responders” who have been sprinting across the city to film arrests, aiming for at least two to arrive on the scene within 10 minutes.

When training volunteers, OCAD instructs them to stay a safe distance from agents and makes clear that their goal is to observe but not intervene or prevent arrests. They share footage with elected officials and lawyers representing those apprehended, but do not post the videos online. And they emphasize that the safety of everyone involved is their top priority. Despite these precautions, Vargas told me that her colleagues, and others doing similar work in Chicago, have been thrown to the ground, pepper-sprayed, and tailed in their cars by officers in an apparent attempt to intimidate them. A few weeks ago, agents temporarily detained some of their members—all of whom are citizens or legal residents—so Vargas and her colleagues quickly removed them from group chats in case their devices were searched.

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To protect themselves and their work, they also keep their office location private and have started to ban phones, laptops, and other devices from meetings.