"He loved his life in Melbourne and he loved his friends - he moved here when he was just 7 or 8.
"He was battling with depression and he didn't really make it known to us," Ms Kahukiwa said.
According to the Age, the incident was described by police as a "definite tragedy", and they have ruled out any suspicious circumstances.
Ms Kahukiwa said Mr Hall and Mr Kahukiwa were extremely close.
Mr Hall, who had two young daughters, also suffered from depression and the pair were able to support each other.
"They loved each other and were loyal to each other."
She said Mr Hall was getting professional help for his mental health problems, but Mr Kahukiwa was not.
She wished her brother had asked for help sooner.
"He didn't start talking about it with us until about four weeks ago," she said.
"Our door was always open for him. But he was just hiding it, he never wanted to burden anyone with what he was going through."
She said the family had planned to help Mr Kahukiwa move back to Gisborne to live with his sister.
"We were taking steps for him to move home, we were planning his 21st in July, he was going to move back to Gisborne - he is coming home now, just not in the way we wanted it to be."
Mr Hall was described by his sister Sophia as a hero, who loved Mr Kahukiwa like a brother, the Herald Sun reported.
"He has always been like that. He is really heroic, has a really good heart and we are just devastated because he didn't want to go: he had two kids and he was a really good dad.
"He did a wonderful thing for the best reasons, to help a friend."
Bring my brother home
The Kahukiwa family is hoping to raise money to return Mr Kahukiwa's body to Gisborne for a funeral, and has set up a Go Fund Me page with a goal of $15,000.
The page has so far raised $5000.
Ms Kahukiwa said she wanted to learn more about depression as a result of her brother's death, and hoped that people would learn how important it was to ask for help when they needed it.
The family will meet the coroner tomorrow morning.
Where to get help
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• If it is an emergency and you feel like you or someone else is at risk, call 111.