“An unclassified summary of the U.S. military investigation into the March 17 incident determined that the 500-pound bomb used in the strike set off additional explosives that were placed in the building by the Islamic State, causing the collapse of the structure.” From WaPo: Pentagon confirms airstrike killed more than 100 civilians in Mosul. (Two Islamic State snipers were also killed in the blast.)

+ NYT: U.S. Airstrikes on ISIS Have Killed Hundreds, Maybe Thousands of Civilians.