The Gunters spoke to Matt in recovery after the operation, which went well. He seemed okay, albeit a "bit grumpy". They also visited him after he was taken to Parfitt Ward.
She kissed Matt goodbye, telling him they would see him in the morning.
"The next morning at 10 to seven we received a call from the hospital saying that Matt had gone into respiratory arrest; he had been found not breathing."
They rushed to Matt's side to find hospital staff had performed CPR on him.
"They were doing an incredible job, they worked on Matt for eight hours to stabilise him before he was flown to Christchurch, where he was admitted to the critical care unit."
Matt left Greymouth on life support. He died peacefully 10 days ago in Christchurch Hospital, with his family and friends by his side.
"Unfortunately, Matt didn't survive, but thanks to the efforts of all the medical staff involved we were given three extra days with him," his mother said.
At this stage no one knew what had gone wrong.
"We can't guess, we need to wait until we get all the facts. But this does not happen to a 15-year-old healthy kid, who has never been sick in his life," she said.
Matt was farewelled in Greymouth on Saturday with a moving ceremony that started with a haka as he was carried into the church. His parents thanked the community and Matt's former schools, Grey Main and Nelson College, for their support.