Susan Conroy was woken on Thursday night by things banging on the roof of her flat, then a popping sound.
She looked out her bedroom window and saw haze in the direction of the end unit of her Campbell St, Wanganui, block of flats. Then she smelled smoke.
She woke her grandsons, 17 and 18, and told them there was a fire and she needed their help. She asked one to grab her phone and ring 111, and the other to knock on doors and wake everyone else in the complex.
Security guards were the first to turn up at the scene, then curious people followed by the fire service and police.
"By this time, the unit was well ablaze. I couldn't see flames, but I could see a glow and hazy smoke," she said.
The occupant of the burning unit was outside it and in "a terrible state". He might have inhaled smoke and Ms Conroy stayed with him until he was taken to hospital in an ambulance.
She is still concerned about his well-being.
Senior firefighter Gary Anderson said the call to the fire service was received at 11.46pm and the place was well involved by the time a fire crew arrived. The fire took 20-30 minutes to put out.
Firefighters then broke into the ceiling and the flat next door, checking for hot spots. They stayed until about 4am.
The flat was totally gutted, Mr Anderson said.
Whanganui fire personnel had spent an hour at another fire earlier in the evening. They were called to a fire in a pile of sawdust in the Rogers and Hinau St area at 7.19pm.