Final answer:
The boss initially reacted with shock and grief when he heard about his son's grave. He called out to his son and begged him to come forth, but the son attacked him in anger.
Step-by-step explanation:
The boss initially reacted with shock and grief when he heard about his son's grave. In the text, it says that the boss groaned and uttered a bitter complaint when he heard a voice that he recognized as his son's. He moved towards his son, calling out to him and begging him to come forth, but the son, filled with anger and grief, spat in his face and attempted to attack him with a sword.