Actually, Aqtaay was killed by the command of Aybak by means of the Mu‘izzi Mamluks on the 3rd of Sha‘baan 652 A.H. With the killing of Aqtai, the field became vacant for Aybak, who soon started to show his power and make his opinion superior, by the time the role of Shajarat Ad-Durr started to weaken. King Al-Mu‘izz had gained the necessary experience for rule, his Mu‘izzi Mamluks became more powerful, the circumstances of the state stabilized, he was approved by his people, his sovereignty was legitimatized by the Abbasid Caliph, and the Ayyubid emirs of Shaam accepted reconciliation with him.

With the death of Aqtaay, the Mamluks were divided into two large opposing parties: the Bahri Mamluks who were entirely loyal to Shajarat Ad-Durr, and the Mu‘izzi Mamluks who were loyal to King Al-Mu‘izz ‘Izz Ad-Deen Aybak.

Whereas Aqtai, the most high-ranking and the most awesome among the Bahri Mamluks was killed, it was more likely that the remaining leaders of the Bahri Mamluks would be killed. The Bahri Mamluks became fearful and skeptical, and their leader, Shajarat Ad-Durr failed to be of any advantage for them. Thus, the leaders of the Bahri Mamluks decided to flee to Shaam for fear of King Al-Mu‘izz ‘Izz Ad-Deen Aybak. The most prominent runaway was Rukn Ad-Deen Baybars who joined An-Naasir Yoosuf, the traitor, who was the governor ofAleppoand, later on, ofDamascus(andAleppo), and submitted to him.

The atmosphere in Egypt became quite clear for King Al-Mu‘izz ‘Izz Ad-Deen Aybak, even though the enmity between him and the Bahri Mamluks exceeded the stage of doubts and expectations and became public and explicit. Once again, the Abbasid Caliph mediated to ensure the stability of circumstances inEgyptand Shaam, since the joining of the Bahri Mamluks to the Ayyubid emirs of Shaam might, more probably, kindle the fire of affliction betweenEgyptand Shaam. The mediation of the Abbasid Caliph succeeded; and they agreed that the Bahri Mamluks would live inPalestine, which was under the control of King Al-Mu‘izz, and King Al-Mu‘izz would be inEgypt. But Baybars, the leader of the Bahri Mamluks after the assassination of Aqtai, preferred to remain inDamascuswith An-Naasir Yoosuf.

https://en.islamstory.com/index.php/en/artical/20809/killing-aqtaay