The detective inspector said a number of inquiries had been undertaken by police investigating the homicide since May 17.
Inquiries are ongoing and police cannot rule out further charges being laid in relation to the homicide.
The man charged with a firearms offence has previously appeared in the Manukau District Court.
Siaosi, also known as Joe, was gunned down in Piako St on Friday.
The operation, dubbed Operation Rye, was launched to investigate the death of the 23-year-old on May 17.
Tuala Tusani told the Herald that his cousin Siaosi was shot by an occupant of a car as he walked away.
Siaosi's friend and the first police officer to arrive gave CPR but Siaosi died on the lawn in front of the family home in Piako St.
"He was shot here in front of his house. It was a drive-by shooting," said Tusani, who was with family who had gathered at the house yesterday.
"There was an altercation between my cousin and the guys in the car.
"It was a normal disagreement [but] I'm just not sure where all the firearms are coming from. It's not like disagreements are new."
His cousin, like a lot of young people, had too much time on his hands, he said, but as far as he knew wasn't officially part of a gang.
"This is his street. This is his home. It was just a fight. My cousin had challenged [someone in the car] to come out and have a man-to-man, and they didn't. They shot him."
On Saturday, Tusani said the family was planning for a funeral and trying to understand what happened.
