Albert Barnes Commentary 2 Chronicles 23:13

"and she looked, and, behold, the king stood by his pillar at the entrance, and the captains and the trumpets by the king; and all the people of the land rejoiced, and blew trumpets; the singers also [played] on instruments of music, and led the singing of praise. Then Athaliah rent her clothes, and said, Treason! treason!" — 2 Chronicles 23:13 (ASV)

At the entering in - That is, at or near the opening from the main chamber of the temple into the Holy of Holies.