When two men bearing federal badges showed up at the entrance of a Chicago public school on Friday morning, school employees did what they had been trained to do.

Believing that the men were U.S. Immigration and Customs Enforcement agents, the employees refused to allow them into the school, John H. Hamline Elementary, which enrolls children in kindergarten through eighth grade in a mostly-Latino neighborhood on the city’s southwest side.

The school immediately notified officials at Chicago Public Schools, which quickly released a statement.

“The ICE agents were not allowed into the school and were not permitted to speak to any students or staff,” the statement said.

But the school was mistaken: The agents were actually from the Secret Service, not ICE. They were investigating a threat against someone their agency had been assigned to protect, relating to the TikTok ban, a Secret Service spokesman said hours later.

The spokesman, Anthony Guglielmi, declined to name the person who was threatened. The agents had gone to a nearby home to try to speak to a minor, and then had tried the school, unsuccessfully.