Just before noon on a sunny Friday earlier this month, federal immigration agents threw tear gas canisters onto a busy Chicago street, just outside of an elementary school and a children’s play cafe. Parents, teachers and caretakers rushed to shield children from the chaos, and have been grappling ever since with how to explain to them what they’d seen: how much to tell them so they know enough to stay safe, but not too much to rob them of their innocence. Weeks later, families — even those not likely in danger of being rounded up in immigration raids — say they remain terrified it will happen again, demonstrating how fear seeps into every facet of American life when the Trump administration’s immigration crackdown takes over a city. Why did the agents tear gas a residential neighborhood?