On the morning of Dec. 5, Wesley Clark Jr., the leader of a loosely formed protest group, Veterans Stand for Standing Rock, woke up to the buzz of his cell phone in a hotel room in the Prairie Knights Casino and Resort in Cannon Ball, North Dakota. It was 6:30 a.m. The caller had some troubling news. Just before dawn, one of the veterans down in the protest camp, where members of the group had bedded down for the night, had apparently disappeared. He was last seen walking in the direction of the Missouri River. There was a suicide note.