Preliminary data based on the notification from the Indonesian authorities:
The aircraft was on a flight from Hong Kong (VHHH) to Jakarta (WIII) as flight GA863. After about 15 minutes airborne, the pilot in command (PIC) was unconscious. The Second in Command (SIC) take aircraft control and decided to return to Hong Kong. There was another company pilot onboard the aircraft.
The SIC asked to the pilot to be in the cockpit. The aircraft landed safety and the ambulance was transferred the PIC to the nearest hospital in Tung Chung area.