He had spoken to Dion's parents, whose names he did not release.
"I express my deepest sympathy from us (police) and the search and rescue crew. We did throw everything at it," Snr Const Johnston said.
Snr Const Johnston said the death would be referred to the coroner.
Victim support services would be offered to the boy's family and friends who witnessed Dion's ordeal.
Snr Const Johnston described the gorge as a fun place to go on a hot summer's day.
"But it does have its hazards. The hydraulics of water in a gorge can easily be underestimated."
Dion's death caps off what Phil Melchior, a Wanaka LandSAR volunteer and chairman of New Zealand LandSAR, said had been a "bad day", for searchers, after a tramper was found dead after a fall near Makarora, and an injured woman was rescued from the Motatapu River.
A helicopter search of the Wilkin Valley, near Mt Twilight, was launched about 3pm yesterday after the 60-year-old man was reported missing by tramping companions.
Senior Sergeant Allan Grindell said details about the man were limited and police were trying to contact his next of kin, overseas.
A Wanaka LandSAR team found the man's body last night, Snr Sgt Grindell said.
Searchers said the man had been climbing during a tramp in the back-country mountain area of Mt Aspiring National Park.
"It appears he has has fallen while negotiating a new route on Mt Twilight," Snr Sgt Grindell said.