The explosion was almost certainly caused by firedamp - the miners' term for pockets of methane gas that accumulate in coal seams and detonate when exposed to a spark or flame. The Royal Commission of inquiry later concluded that a blown-out shot in a section of the mine where no one should have been working was the trigger. But the initial blast was only the beginning. In the confined tunnels, the explosion generated afterdamp - a lethal mixture of carbon dioxide, carbon monoxide, and nitrogen that filled the passages behind the fireball. Joseph Scott, the Blackball Mine Manager, believed most of the men died from the explosion itself. Robert Russell thought otherwise, arguing that 'at the end it was the afterdamp gases that killed them all.' Dr. James McBrearty noted that many victims were found frothing at the mouth, a sign of asphyxiation by carbon dioxide.

Rescuers rushed into the mine and were driven back by the afterdamp, some collapsing unconscious and having to be carried out by other rescuers who then succumbed themselves. Word spread across the West Coast, and miners came from as far as Denniston to help - though the Denniston men had to travel by sea from Westport, a journey that took several days. These were not strangers answering a call for volunteers. The West Coast mining communities of the 1890s were bound by what historians describe as occupational loyalties and kinship ties. Denniston miners, Blackball miners, and Brunner miners shared workmates, relatives, and friends from the same generation of immigrants. The miners' code demanded they come to each other's aid. They came knowing what they would find.

News of the disaster spread across New Zealand and prompted an outpouring of support. A disaster relief fund was established for the families of the 65 dead miners, and contributions arrived from towns across both islands - Auckland, Nelson, Christchurch, Lyttelton, Invercargill. Over 32,000 pounds was raised, a substantial sum that reflected both the scale of the tragedy and the national recognition that these men had died doing work that powered the colony's economy. A Royal Commission was appointed to investigate: district court judge Charles Ward, geologist Sir James Hector, colliery manager Joseph Proud, and coal miner Thomas Skellon. They reported to the Governor-General on June 15, 1896, less than three months after the explosion.

The Brunner Mine site sits in the Grey Valley near the small settlement of Brunnerton, surrounded by the kind of dense West Coast bush that reclaims human works quickly. The mine closed after the disaster and the forest has had more than a century to grow back over the workings. But the site has not been forgotten. A memorial marks the location, and a folk song - 'Down Brunner Mine' - keeps the story alive in a region where mining disasters are not abstract history but family history. The Pike River Mine explosion of 2010, which killed 29 men in the same West Coast region, drew immediate comparisons to Brunner. One hundred and fourteen years apart, the parallels were unmistakable: men underground, an explosion, poisonous gas, rescue attempts that could not reach them in time.