New York City Mayor Bill de Blasio warned Thursday that Donald Trump’s support for allowing police to stop and frisk people they think are suspicious would lead to even more civil unrest.

“You know Donald Trump talks about stop-and-frisk like he knows the facts, he has had no experience with policing, he has no experience with public safety,” de Blasio said during a Thursday interview on CNN. “He should be really careful because if we reinstitute stop-and-frisk all over this country, you would see a lot more tension between police and community.”