A U.S. Border Patrol agent has been accused of assaulting a 15-year-old immigrant detained in Arizona. The agent, identified as Aldo Arteaga, 35, faces charges of aggravated assault, after an incident on Jan. 30.

While it’s not the first time this happens, what is particularly shocking is the victim’s age. The incident takes on additional significance since thousands of unaccompanied minors from Central America have entered the United States since October 2013, many of them fleeing violence and abuse.

The investigation is being handled by the Border Patrol's Office of Internal Affairs.