"It was only after that game ended that Brunning's condition deteriorated and doctors and paramedics began working on him frantically.
"He did not respond to repeated attempts to revive him," NRL reported.
Brunning was a former student of Illawarra Sports High School, where he earned selection in the Australian Combined High Schools team.
Country Rugby League and Illawarra Division Rugby League extended their sympathies to Brunning's family, friends and teammates.
Illawarra District Rugby League general manager Chris Bannerman said it was a tragedy no family should have to go through on the eve of Mother's Day.
"It appears to be a terrible tragedy and we extend our sympathies to his family and friends, and everyone who was involved yesterday at the venue," he said.
"We've been working with the CRL and NRL to provide welfare support to players and others associated with both clubs. That's already started and we'll be continuing with it," NRL reported.
A Givealittle page has been set up for Brunning by his aunty to bring his body back to New Zealand.
She said he moved to Australia about seven years ago to chase his dream of playing league at a competitive level.
A service would be held for Brunning in Wollongong and then it was his family wish to return him back to his home of Waitara in the Taranaki region.
The funds would be used to pay for the expenses involved in transporting Tory from Australia to New Zealand.