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.

In a letter to families Wednesday, officials with the Acero charter school network said the individual was taken into custody by ICE agents, though the agency itself did not respond to a request for comment.