2 Kings 12:20

And his servants arose, and made a conspiracy, and slew Joash in the house of Millo, which goeth down to Silla.

Joash was the true king of Judah, hidden until he was old enough to be proclaimed king after Athaliah usurped the kingdom of Judah, after which Athaliah was slain. His reign began under the guidance of the good priest Jehoiada. As a young king, Joash repaired the house of God in Jerusalem with money gathered from the people for the work, in a similar way to Josiah two centuries later.

His reign included submission to Hazael. The verse records the death of Joash king of Judah, closing the account of his reign. The chapter belongs to the continuing record of the kings in which Judah has now and then good kings while the kings of Israel are invariably weak or altogether bad. The 2 Kings 9-12 portion to which the verse belongs continues the story of the reign of weak and wicked Ahab.