CHICAGO — When U.S. Immigration and Customs Enforcement arrested Irma Rodríguez-González, a cashier at a mini-mart in Chicago, at her work in August, they weren't weren’t acting alone. They were brought there by officers from the Chicago Police Department.

"When they were taking my information, I heard someone say that Homeland [Security] was there," Rodríguez-González said. "[The ICE agent] asked me to show him my green card. And I said that, well, that I didn't have one."

Rodríguez-González has lived in the U.S. for 25 years. She has three American-born children and no criminal record. And her arrest — executed by ICE but directly facilitated by the police — is exactly the kind of thing that’s not supposed to happen in a sanctuary city like Chicago, which prides itself on trying to be “the most immigrant friendly city in the country.

So how did her arrest come to pass?

In Chicago, as in many other major sanctuary cities, the police still routinely work on joint task forces with Homeland Security Investigations, the unit of ICE that investigates transnational crimes. Typically, these task forces target suspected gang members or terrorists. In Chicago, the operation that netted Rodríguez-González focused on stores suspected of selling fake sports jerseys and other counterfeit goods.

Under the Trump administration, ICE is above all a deportation force, and its agents are under orders to detain any undocumented person they encounter in the course of their work — regardless of whether they’re suspected of a crime.

That’s what happened to Rodríguez-Gonzalez. But in spite of this fact, Democratic officials — even those who are among the biggest champions of sanctuary policy — are unwilling to sever the ties their police departments preserve with ICE. And that has neighborhood residents on edge.

"If I feel that calling the police is going to lead to my detention or my family's detention, why would I do that?" said Eréndira Randón, a DACA recipient that works at a nonprofit that helps immigrants in the community.

This segment originally aired September 12, 2018 on VICE News Tonight on HBO.