The way in which he succeeded to the sultanate is the following:

When they returned from praying over al-Malik al-Ẓāhir Khushqadam, they sat at the Bāb al-Sitār for a short while, when suddenly amir Khayrbak came out from the Bāb al-Ḥarīm, accompagnied by a number of his khushdāsh. They took ʾatābak Yilbāy, took him through the Bāb al-Ḥarīm up to the Qaṣr Sulṭānī, and addressed him on the matter of the sultanate. He turned it down gently, but they paid no attention to what he said. They then sent for the amirs, summonning them to come to the Qaṣr from outside. However, they found the Bāb al-Qaṣr to have collapsed. Hence, they entered the Qaṣr by way of the ʾīwān. The fact that the Bāb al-Qaṣr was locked was considered a bad omen by the people, an omen of the speedy end of his rule.
The amirs had come in before the caliph and the qadis.