2 Chronicles 23:15

So they laid hands on her; and when she was come to the entering of the horse gate by the king’s house, they slew her there.

Cross-reference

2 Chronicles 22:10 describes Athaliah's murderous usurpation — the backstory leading to her execution here.

2 Kings 11:16 is the parallel account of Athaliah's execution — almost identical details of her seizure and death at the horse entrance.