The tragedy occurred on Thursday afternoon on 3/F of Lok Tung House in Lok Fu Estate as the boy was playing with the incense sticks, which accidentally set fire to the curtain on the neighbor's door.

Acrid smoke billowed from the unit after the blaze was started, and the 66-year-old woman was found lying on the floor of the living room when rescued by firefighters.

She had lost consciousness and was rushed to a hospital. She remained in critical condition and eventually passed away on Friday night.

A 34-year-old Filipina domestic helper was admitted to the hospital in a conscious state after inhaling the smoke.

The boy was arrested that day by police for arson and is still in custody. The case is now handled by the Wong Tai Sin district crime squad.

The boy lives with his younger brother, and the duo is taken care of by an aunt, who said his parents have learned their son has been taken away by the police.

The aunt said she didn't feel so well because she didn't know what had happened, including the actual cause of the fire. She had yet to contact the deceased's family and only hoped the two children could be safe and well.

She continued that the two children were playing in the corridor at that time as usual and admitted her negligence. Yet, she noted she was doing chores and would check on the kids every few minutes.

Another neighbor – a woman surnamed Wong – said she didn't know how the fire started. She recalled she was sleeping in her room and found smoke filling her unit after her daughter smelt of burning.

She immediately grabbed her two kids, fled the scene, and reported to the police.