He was out on bail for throwing killer litter when he committed the same offence again - this time with tragic consequences.

Abdul Hamid Rahmat, 16, built a contraption to launch a bicycle wheel from the 14th storey of Block 1, Eunos Crescent at about 2.15pm on May 16 last year.

The wheel landed on Madam Mahani Abdullah's head as she was walking near the void deck. The 67-year-old retiree died in hospital.

Abdul Hamid's earlier killer litter offence occurred on Aug 24, 2013, when he threw two ceramic tiles, a 5kg dumbbell and a water dispenser from the 11th to 13th storeys of Block 1, Eunos Crescent, where he lived.

About four months later, he threw a brick from the 12th storey of the block and it hit Mr Kyi Phyu Phyo Wai's hand as the 25-year-old man was walking on the pavement below.

The police were alerted and officers arrested the teenager four days later.

Abdul Hamid was soon released on bail.

The teen caused grievous hurt to Madam Mahani on May 16 last year and was arrested the next day.

For each count of causing grievous hurt by performing a rash act, he could have been jailed up to four years and fined up to $10,000.