A 16-year-old boy also suffered a stab wound to the leg but has since recovered.

After multiple appeals for information and a lengthy investigation, police have arrested three teenagers over the past week.

An 18-year-old man was arrested at a Shalvey home last Saturday and has been charged with murder.

A second 18-year-old man was arrested at Schofields Train Station on Wednesday and has been charged with murder.

A 14-year-old boy was arrested in Arndell Park on Friday and has also been charged with murder.

Acting Assistant Commissioner Jason Weinstein said police will allege the 14-year-old boy is "the individual who inflicted the stab wound to the victim at the Easter Show".

All three teenagers have been refused bail and remain before the courts.

Weinstein said the three accused and the victim were known to each other.

Weinstein added officers believe there are others involved in the attack.

"There are still other individuals who we know that were party to this offence," he said.

"If you are one of those individuals who was there at the time of the offence at the Easter show, I implore you, go to your local police station and hand yourself in.

"We will not rest until every individual involved in this matter is currently before the courts."

Weinstein said police have been met "with a wall of silence" while investigating this murder.

"This and other recent acts of knife crime that we've seen were senseless acts of violence which have had devastating consequences for victims, their families, and also those allegedly responsible," Weinstein said.

"I don't want to see other families devastated like this."

Deputy Premier Paul Toole said this week's breakthrough in the case sends a strong message against knife violence.

"The incident we saw at the Royal Easter show this year was shocking and it was violent," Toole said.

"It doesn't matter what age you are, you will be charged and you will be caught if you are engaged in any sort of activity like this."