"Just as the king returned from the palace garden to the banquet hall, Haman was falling on the couch where Esther was reclining. The king exclaimed, 'Will he even molest the queen while she is with me in the house?' As soon as the word left the king's mouth, they covered Haman's face." NIV translation
Haman was out of his mind as he faced certain death. He was begging the queen to intercede on his behalf and even fell on the couch where she was laying. When the king returned and saw that, it was all that he could stand and Haman was seized.
"Then Harbona, one of the eunuchs attending the king, said, ' A gallows seventy-five feet high stands by Haman's house. He had it made for Mordecai, who spoke up to help the king.' The king said, 'Hang him on it!' So they hanged Haman on the gallows he had prepared for Mordecai. Then the king's fury subsided." NIV translation
In his anger, Haman had built this gallows to make a public example of Mordecai. This same anger at the Jews also caused him to offend the king. Now, he is hanged on the very gallows that he had built in anger. This is a reminder to us today that God is love and, since we are His children, we do not have any room in our hearts for this type of anger and hatred.
This is also what Paul told the Ephesian believers when he told them to live as children of light (see Ephesians 5:1).