Iraqi officials say they are close to victory in an Iranian-backed offensive to reclaim the city of Tikrit from the self-proclaimed Islamic State. Iraqi forces and Shiite militias have reclaimed swaths of the city without the aid of U.S. airstrikes. The gains come as ABC News reports Iraqi military units trained and armed by the United States are under investigation by the Iraqi government for war crimes. Videos and photos on social media appear to show militia members and soldiers from elite units massacring and torturing civilians and displaying severed heads.