2 Kings 11:14
And when she looked, behold, the king stood by a pillar, as the manner was, and the princes and the trumpeters by the king, and all the people of the land rejoiced, and blew with trumpets: and Athaliah rent her clothes, and cried, Treason, Treason.
The king in view is Joash, taking his place beside the customary pillar at the public ceremony by which he is recognized as king. The princes and the trumpeters are stationed beside him, while all the people of the land rejoice together and sound their trumpets. Athaliah looks on at the ceremony, rends her garments, and raises the shout of treason. That rejoicing is the acclamation of the surviving rightful heir following her rule, so her accusation has no foundation.