"It was huge. The flames were a couple of storeys high," he said.
A few minutes later the front of the building came crashing down on to the footpath. A woman was near hysterical, wrongly believing her children were inside, and had to be calmed by her partner.
When Tautoko FM hit the airwaves in 1987 it was just the second iwi radio station in the country, the first to broadcast in FM and the first in Northland. It is run by Te Whare Awhina o Te Iwi Charitable Trust, whose chairman, Hori Chapman, said they were saddened by the loss of history but already looking to the future.
"It could be seen as a setback, but we see it as a new start," he said.
"We want to rebuild our whare and expand our services based around our vision."
That vision included giving iwi a voice, improving well-being, and promoting te reo and tikanga Maori.
The station's archive, a treasure trove of historic recordings from Waitangi Tribunal hearings, had been moved into a container just a month earlier and was undamaged.
Mr Chapman said he was keen to rebuild in Mangamuka. It was not an urban centre but was central to much of the Far North. The trust had created jobs there, and many who had started at Tautoko FM had gone on to careers in television.
The building was insured but any payout was unlikely to cover recent renovations. Trustees were considering a fundraising appeal.
Fire investigator Michael Champtaloup said the blaze had started at the rear of the building, possibly in the computer server room, possible culprits including a server, air-conditioning unit or multibox.
The fire had still been relatively small when a shop owner called 111, but by the time the first firefighters arrived from Okaihau 23 minutes later the entire building was consumed. It would have been deadly to anyone inside within five minutes, he said.
The building was not fitted with smoke alarms.
"Alarms might have picked up the fire early enough to save the building. It was an important building to the community, and they've lost a lot of history," Mr Champtaloup added.
Fire Service volunteer support officer Colin Kitchen said three appliances and two tankers from Okaihau, Kaitaia, Kohukohu and Kaikohe responded. Twenty firefighters using breathing apparatus took about an hour and a half to extinguish the flames.
The volunteers had done a great job of saving the adjacent buildings, Mr Kitchen added.
- Police are also trying to determine the cause of the fire. Anyone who saw anything unusual in the area of the radio station building on Monday evening is asked to call Detective Sergeant Chris Fouhy at the Kaikohe police station on (09) 405-2960, or Crimestoppers, anonymously, on 0800 555-111.