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.
The police investigation into Justin’s death is ongoing.
Anyone with information about Justin’s death has been urged to contact Crime Stoppers on 1800 333 000.
More to come
Matt Bungard is a journalist at The Sydney Morning Herald.