A tragic crash involving two school buses in Knoxville, Tennessee, killed two children and one adult Tuesday afternoon and injured another 27 people, most of them young children. The horrific event has left the entire community in mourning. Two buses were bringing school children home on a Tennessee highway when one bus reportedly made a sharp left turn and crossed over a concrete median, hitting the second school bus that was traveling in the opposite direction. The crash caused the second bus to flip onto its side and slide, according to several media reports. The children who were tragically killed were in the third grade or younger and the adult was a teacher's aide, according to reports. As many as 20 other children were treated at area hospitals. Witnesses reported that people were running out of their cars to help. The superintendent of one of the schools involved called the event "an unspeakable tragedy." Investigators from the National Transportation Safety Board (NTSB) reportedly are on the scene to investigate the cause of this terrible crash.