2 Chronicles 22:8-10

New King James Version

⁸ And it happened, when Jehu was ^(A)executing judgment on the house of Ahab, and ^(B)found the princes of Judah and the sons of Ahaziah’s brothers who served Ahaziah, that he killed them. ^9 (C)Then he searched for Ahaziah; and they caught him (he was hiding in Samaria), and brought him to Jehu. When they had killed him, they buried him, “because,” they said, “he is the son of ^(D)Jehoshaphat, who ^(E)sought the Lord with all his heart.”

So the house of Ahaziah had no one to assume power over the kingdom.

Athaliah Reigns in Judah^(F)

^10 (G)Now when Athaliah the mother of Ahaziah saw that her son was dead, she arose and destroyed all the royal heirs of the house of Judah.