It was a beautiful day, and Mary had just gotten home with her new horse, so she decided to go for a ride. She had spent several days, before purchasing the horse, riding and getting to know him and felt confident of his stability. When Mary went to saddle him, he reared back on his halter rope, broke loose and ran away. Mary was startled and surprised. Even though she had never saddled a horse on her own, she had seen it done many times at the riding stable.
What happened?