Two students were with the adult outside the Southwest Side school Wednesday morning, officials said. "It is really terrifying for families and traumatizing for students," one observer said.

Acero Schools officials say the adult was picked up with two children in their car. U.S. Immigration and Customs Enforcement officials did not immediately confirm the action.

Administrators said they escorted two students into the building away from the incident. The federal agents did not enter the building, charter officials said. Federal immigration authorities did not confirm the action.