i would have applied full break as well...that's why it is mandatory to keep a distance between cars, and not to overspeed. And what if it was a cat/dog? and what if it was a child? the driver who was behind is an idiotic driver, since he thinks it's ok to push the car in front of him, and since he assumes it is ok not to be alerted any moment on the road..

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“You become responsible forever for what you have tamed”. Antoine de Saint-Exupéry