First off, I know the headline says Amish tour bus, and that's an odd thing to say if you don't know the story. They were touring other farms in the area, which aparently is cool with their culture.
Anyway... this guy was drunk and tried passing a farm tractor on a curve, with a double yellow line. When he did that he slammed into the tour bus, killing a few Amish and hurting many more.
Turns out he has a lengthy criminal record. I know, shocking right?