Preliminary investigations found that the 16-year-old suspect bought the axe online.
This was revealed by Minister for Home Affairs and Law, K Shanmugam in a Facebook post on July 20.
In his post, Shanmugam called the incident "completely shocking", and said:
"One of the worst things that can happen to parents is to hear, from school, that their child has been killed."
He also added that the "full facts" will be known after investigations are complete.
During court proceedings today when the suspect was charged with murder, the Attorney-General Chambers told the court that he has a history of mental health issues.