I just received a message from one of my friend, who is also a good friend with the deceased. What I heard from his story was, the deceased was on expedition on Mount Kinabalu for more than one week. They planned to climb Eastern Plateau (Kotal Route) and Western Plateau (Gurkha Hut) during their expedition. However, the deceased succumbed to acute mountain sickness.
*The risk of death from acute mountain sickness is very minimal if you are climbing the ordinary tourist track of Summit Trail and Mesilau Trail. Anyway, please be careful. The mountain can be very dangerous.
Rest in peace, Khairuz Elfi Mansor.