Al-Hakim had installed an astronomical observatory on Jabal al- Muqattam, near Cairo for Ibn Younus. According to Ibn Khallikan, al- Hakim went out late in the night of 27th Shawal, 411/February 13, 1021 to Jabal al-Muqattam and did not return to the palace. A tracking party was sent out, who found an ass on the top of the hill with its forelegs hacked off. Blood marks on the ground led to a spot, where they found al-Hakim's clothes pierced by daggers and buttoned up, and as such his death was officially declared on 10th Zilhaja, 411/April 4, 1021. The Druzes however believed that al-Hakim did not die but disappeared, anticipating his return on dooms-day. He died at the age of 36 years and 7 months after the Imamate and Caliphate of 25 years and 1 month. Makrizi (2nd vol., p. 290) quotes one other tradition about al-Hakim's death on the authority of Abul Mahsin that in 415/1025, a man from Imam Hussain's family had been arrested after raising up rebellion in the southern part of upper Egypt. He confessed that it was he who had killed al-Hakim. He said that there were four accomplices of the crime, and that they afterwards fled to different parts. He also showed a piece of cotton with which he had been clothed.
Imam al-Hakim had two sons, al-Harith (395-400/1004-1009) and Ali Abul Hasan, surnamed az-Zahir. He had also a daughter, Sit al-Misr (d. 455/1063).
Muhammad bin Ali as-Suri (d. 488/1095) praises al-Hakim in his poem (vide "al-Qasida as-Suriyya," ed. Arif Tamir, Damascus, 1955, p. 68) in the following words:-
The perfect resides wholly in the ninth (Imam). In him the parturition is accomplished, the coming to light is done. And the conceal and hidden appear. In al-Hakim God established His Will in the world, and the wisdom of the Just was realized.