A 13-year-old boy has been arrested for allegedly throwing two bricks from the 12th floor of an HDB block.
Police were alerted to the latest in a spate of "killer litter" incidents on March 17, when the bricks were hurled from Block 116, Jalan Bukit Merah. No one was injured.
Following investigations, officers from Bukit Merah East Neighbourhood Police Centre arrested the teenager on Tuesday.
The Straits Times understands that the suspect was captured on a private CCTV camera lobbing the bricks from a corridor.
Police said they are investigating the boy for performing a rash act which endangers life or the personal safety of others.
This comes after two brothers, aged 10 and 11, were arrested last December for allegedly throwing a small speaker and a vehicle battery from their Dover Road flat.
Four days earlier, a 15-year-old boy was arrested for allegedly throwing a brick from his Eunos Crescent flat, injuring a passer- by.
The teenager is also being investigated for his alleged involvement in previous killer litter cases in his estate involving a dumbbell and a water dispenser.
All three suspects have been released on bail. Police told The Straits Times last night that both cases are still being investigated.
Experts say such behaviour can be caused by factors such as rebelliousness, immaturity and underlying mental or developmental problems.
Dr Adrian Wang, a consultant psychiatrist at Gleneagles Medical Centre, said youngsters who carry out such acts often have "no respect for authority" and a lack of remorse, as well as display impulsive behaviour which can be worsened by substance abuse.
"Their understanding of long- term consequences is also not like an adult's, that it may cause harm to others or have an impact on future employment."
Other explanations include mental illness such as psychosis.
"Such teens could become very agitated because they are hearing voices or fearing that people want to hurt them," said consultant psychiatrist Ken Ung of Adam Road Medical Centre.
A person with developmental problems like autistic spectrum disorder or attention deficit hyperactivity disorder can be set off easily, he added.
"They can become severely agitated - it just needs a little thing to set them off."
The offence of causing a rash act carries a maximum punishment of six months in jail or a fine of up to $2,500, or both.
Criminal lawyer Josephus Tan said courts usually seek to rehabilitate juvenile offenders, either via probation or detention in a home.
Should the act kill somebody, even inadvertently, the punishment can be much more severe.
Criminal lawyer Amolat Singh said: "Rehabilitation is always the greater priority, but let's say a youth threw bricks and killed somebody - he could be detained at the President's pleasure without a fixed period of time."