He did day to the kids “Are you ready to die?”
According to the news report at the time, one mother of a child that was one the bus stated that her child said he said “are you ready to die?” just before he went around the sharp curve and crashed.
Another report, which has mostly been ignored, stated that he had DEVIATED FROM THE SCHEDULED ROUTE.
Even the NY Post had that: http://nypost.com/2016/11/22/bus-driver-asked-kids-if-they-were-ready-to-die-before-crash/