The Iranian elementary school building where scores of children were killed as the U.S. and Israel began their massive aerial campaign was on a U.S. target list and may have been mistaken for a military site, multiple people familiar with the strike told The Washington Post.

The deadly attack occurred in the first few hours of the U.S.-Israeli war against Iran — just as parents were hurrying to the two-story schoolhouse to take their kids home to safety — and killed at least 175 people, many of them children, according to Iranian state media.