In section one of the sweet hereafter, what events foreshadowed the accident for dolores

There were two events that I remember in section one:
1. When Sean Walker gets on the bus and suddenly gets frightened, he doesn't want to leave his mother. It was only with the help of Nichole Burnell that Dolores was able to calm him down and persuade him to sit with them in the bus.
2. While Dolores was driving to the poorest part of the community, she saw a stray dog and hits the brakes to avoid it. Even though there was no danger, she feels frightened. 

On a difficult stretch of Barlett Hill Road, she believes she'd seen another stray dog and swerves. The bus moved swiftly off the side of the road and into the icy water.