So she committed suicide by truck. How considerate of her. She was selfish to the end, not giving a second thought to what might happen to the driver of the truck.
This is sad.
It’s sad for the mother who loved her son.
It’s sad for the truck driver who will relive the horror over and over again.
And, yes, it’s sad for this teenage boy, but he made a choice to destroy two people - his mother and a stranger - along with himself. His mother simply told him the truth and loved him.