Abdirahman Sheik Mohamud is shown in a Columbus, Ohio, courtroom in 2015. He was arrested after traveling to Syria, then returning to Ohio, where he planned to carry out an attack. According to a new report, he's one of 12 Americans who went to join extremist groups in Syria or Iraq, and then returned back to the U.S. Mohamud was sentenced last month to 22 years in prison. (AP)
