Commander of the NSW Homicide Squad, Detective Superintendent Scott Cook, said Justin had suffered «significant injuries» over a long period of time before he was killed.
«He was physically assaulted for hours and hours and hours, so you could say it’s torture,» he said.
«He had defensive injuries, and there’s some suggestions that he actually was pleading for his life.»
Superintendent Cook said police believed his death stemmed from a property dispute of «little value».
«The fact that it was perpetrated by such young people against each other is an absolute shame,» Superintendent Cook said.
«It’s very concerning in a sense that if the underlying motive is a property dispute, how can that escalate to torture?»
Mr Tsang’s body was found four days after he was reported missing, at Wentworth Falls in the Blue Mountains.
Police said Mr Tsang had been bashed and stabbed before his body was buried at a lookout.
On Wednesday, police arrested four men — three 18-year-olds and a 19-year-old — at a home in Burwood Heights.
Two of the 18-year-old men were charged with murder, and take or a detain a person with intent to obtain advantage occasioning actual bodily harm.
Police will allege in court that the two men – who knew Justin — picked him up from a Drummoyne home on March 12, before seriously assaulting and stabbing him to death at a Burwood Heights property and burying his body at Wentworth Falls.
The 18-year-olds were refused police bail, and are due to appear in Burwood Local Court on Thursday.
The other men who were arrested, aged 18 and 19, were released without charge, and police said their investigations were ongoing.
A fifth man, aged 19, was arrested at Bankstown police station on Wednesday night.
The Punchbowl man was charged with murder, and take or detain a person with intent to obtain advantage occasioning actual bodily harm. It will be alleged in court that he organised and coordinated the murder of Justin.
He was refused police bail and is due to appear in Bankstown Local Court on Thursday.
Superintendent Cook said officers were on Thursday continuing to search a Burwood Heights property for evidence.
«We are gaining significant evidence out of that crime scene, and that will inform future investigations as will information that comes from the public,» he said.
«We will gladly receive any information in regards to what occurred.»
The police investigation into Justin’s death was ongoing.
Anyone with information about Justin’s death has been urged to contact Crime Stoppers on 1800 333 000.
Matt Bungard is a journalist at The Sydney Morning Herald.
Rachel Clun is a journalist at The Sydney Morning Herald.