Liam's mum had been in Reporoa visiting relatives in the days before he got sick.
"It happened so quickly. Last Monday doctors sent him home with antibiotics, Sarah flew back Tuesday and noticed he was still not looking right so took him back and he didn't come out of hospital," Ms Heads said.
She said the "horrendous virus" attacked Liam's organs and he was put on bypass machines to give them a break "but it was just too aggressive".
Ms Heads said the family made the heartbreaking decision to turn off the machines on Friday night. Liam was a fit and healthy teenager who loved all sports, she said.
"It was just bad luck."
While Liam was young when he moved to Australia and it was his home, he knew he was from the Rotorua and Reporoa areas and had been back "heaps", she said.
"The wider family have taken it harder because it happened so quick. His mum is thinking of everyone else before herself and Liam was exactly the same."
Ms Heads said she would remember Liam as incredibly caring, but also cheeky.
"He would give you the shirt off his back for you to stay warm. He was cheeky, but never disrespectful."
Ms Heads said what upset them the most was that it always happened to the good kids.
"This is what we are all struggling with. Why him?"
Ms Heads said tomorrow's service was a way for those who couldn't afford to travel to his funeral in Australia to get together and remember him, and support extended family.
The service is being held at 3691 State Highway 5 at 1pm. All are welcome.
The Gold Coast Bulletin reported the area was in the midst of a significant influenza outbreak which had left a disproportionate number of teens with pneumonia.