Yau Tsz-lam, a former student at Wai Chow Public School (Sheung Shui), won silver in the 50-metre butterfly, and gold in 200m breaststroke in the morning. The avid swimmer clocked three minutes and five seconds in his breaststroke final, beating the old record by more than 20 seconds.
In the early afternoon, he participated in the 400m medley relay, winning another gold medal.
Tsz-lam then leapt into the cool-down pool, but started struggling. He was rescued by lifeguards on duty, and rushed to the Prince of Wales Hospital's Intensive Care Unit.
The reasons behind the incident remain unclear; the Form One student has been training since a young age. But it is believed that Tsz-lam could have hit the bottom of the swimming pool while jumping in, causing him to choke in the water.
In the same event last year - which is co-organised annually by the Leisure and Cultural Services Department and the North District Sports Association - Tsz-lam took home one gold and three silver medals.
Police do not suspect foul play.