For Athalia his mother, seeing that her son was dead, rose up, and killed all the royal family of the house of Joram.

And when Athaliah the mother of Ahaziah saw that her son was dead, she rose up and exterminated all the royal seed of the house of Judah.

And Athaliah mother of Ahaziah hath seen that her son is dead, and she riseth and destroyeth the whole seed of the kingdom of the house of Judah.

Now when Athaliah, the mother of Ahaziah, saw that her son was dead, she had all the rest of the seed of the kingdom of Judah put to death.

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

For indeed, his mother, Athaliah, seeing that her son had died, rose up and killed the entire royal stock of the house of Jehoram.

Compare the marginal reference and notes.

All the seed royal of the house of Judah - Nothing but the miraculous intervention of the Divine providence could have saved the line of David at this time, and preserved the prophecy relative to the Messiah. The whole truth of that prophecy, and the salvation of the world, appeared to be now suspended on the brittle thread of the life of an infant of a year old, (see 2-Chronicles 24:1), to destroy whom was the interest of the reigning power! But God can save by few as well as by many. He had purposed, and vain were the counter-exertions of earth and hell.

But when Athaliah the mother of Ahaziah saw that her son was dead, she arose and (h) destroyed all the seed royal of the house of Judah.
(h) So that there would be no one to claim the crown and so she might usurp the government.

ATHALIAH, DESTROYING THE SEED ROYAL SAVE JOASH, USURPS THE KINGDOM. (2-Chronicles 22:10-12)
Athaliah . . . arose and destroyed all the seed royal--(See on 2-Kings 11:1-3). Maddened by the massacre of the royal family of Ahab, she resolved that the royal house of David should have the same fate. Knowing the commission which Jehu had received to extirpate the whole of Ahab's posterity, she expected that he would extend his sword to her. Anticipating his movements, she resolved, as her only defense and security, to usurp the throne and destroy "the seed royal," both because they were hostile to the Phœnician worship of Baal, which she was determined to uphold, and because, if one of the young princes became king, his mother would supersede Athaliah in the dignity of queen mother.

The six years' tyranny of Athaliah. - In regard to her, all that is stated is, that after Ahaziah's death she ascended the throne, and caused all the royal seed of the house of Judah, i.e., all the male members of the royal house, to be murdered. From this slaughter only Joash the son of Ahaziah, an infant a year old, was rescued, together with his nurse, by the princess Jehoshabeath, who was married to the high priest Jehoiada. He was hidden for six years, and during that time Athaliah reigned. The same narrative, for the most part in the same words, is found in 2-Kings 11:1-3, and has been already commented upon there.