When Athaliah the mother of Ahaziah saw that her son was dead, she proceeded to annihilate all the royal heirs of the house of Judah.

2 Kings 11:1
When Athaliah the mother of Ahaziah saw that her son was dead, she proceeded to annihilate all the royal heirs.

2 Chronicles 22:11
But Jehoshabeath daughter of King Jehoram took Joash son of Ahaziah and stole him away from among the sons of the king who were being murdered, and she put him and his nurse in a bedroom. Because Jehoshabeath, the daughter of King Jehoram and the wife of Jehoiada the priest, was Ahaziah's sister, she hid Joash from Athaliah so that she could not kill him.

2 Chronicles 23:15
So they seized Athaliah as she reached the entrance of the Horse Gate to the palace grounds, and there they put her to death.

But when Athaliah the mother of Ahaziah saw that her son was dead, she arose and destroyed all the seed royal of the house of Judah.