Police are investigating why a 13-year-old boy in his school uniform jumped from the ninth floor of a residential building in a Sheung Shui estate. The boy, surnamed So, was found unconscious on the second floor of Ping Chi House in Tai Ping Estate at 5.40pm. He was rushed to North District Hospital, where he was later confirmed dead. His family said he had been upset lately. Separately, a 20-year-old jumped to his death in Choi Mui House, Choi Ming Court in Tseung Kwan O, at 8.20pm.