2 children going home from a Head Start program in Carroll County, Ky., died when the school bus they were in overturned and hit a tree, state police said. Kentucky State Police said four other children were airlifted to hospitals and three students were released to their parents after the accident Monday, The (Louisville, Ky.) Courier-Journal reported. \"It\'s the worst thing you can imagine,\" Kentucky State Police spokesman Brad Arterburn said. Nine children and two adults were aboard the bus. State police said the cause of the accident was under investigation. The sheriff\'s office said another vehicle was involved, but no other details were available. However, state police said they didn\'t know if another vehicle was involved because no other vehicle was at the scene when they arrived, The Courier-Journal said. State police said weather did not appear to be a factor, but did not know whether speed may have contributed.