One night last November, Courtney Partridge-McLennan said goodnight to her family in Australia and went to sleep in her room.
At some point in following hours, the 19-year-old woman suffered a suspected asthma attack. When her parents checked on her the next morning, Courtney had died.
Her family believes that Courtney's death in Glen Innes, New South Wales, was triggered by smoke from nearby bushfires. Like many populated areas across Australia's east, the town has been shrouded by smoke in recent months.
"She was found with her phone torch on, as though she was looking for something," her sister, Cherylleigh, told the BBC's Outside Source programme. "Her Ventolin [inhaler] was on the bed with her."
Courtney was diagnosed with asthma as a child. It was not usually severe but tended to flare up around dust and air pollutants, according to her sister.
"She had no symptoms before she went to bed," Cherylleigh said.
"She was healthy and that's what made it the biggest shock for us. It was so out of nowhere."
Cherylleigh said preliminary autopsy reports had listed the cause of death as "unconfirmed". But she added her parents had been told that Courtney had a "hyper-extension of the lungs" - one indicator of an asthma attack.
"Initially when they found her, the comments were, 'oh it definitely looks like an asthma attack, it looked like it happened really quickly,'" Cherylleigh said.
According to health officials, asthmatics are particularly vulnerable in Australia's ongoing bushfire crisis. The condition narrows a person's airways when triggered by irritants in the air.
In recent months, cities including Sydney, Melbourne, Canberra and Adelaide have recorded some the worst air quality readings globally.
In rural communities closer to the fire-zones, the impact has been even greater.
A fortnight before Courtney's death on 28 November, bushfires ripped through Glen Innes, causing the deaths of two people.
But fires had burned in the region since September, and smoke continued to affect the town afterwards. Her family believes this was the trigger for her asthma attack