No one was prepared for it. Families slowly walked through the Greymouth council car park yesterday afternoon, many holding hands, for their tenth briefing since an explosion at the Pike River coal mine trapped 29 of their loved ones underground.

For six days, they had heard officials talk increasingly of fading hope, saying that with each passing hour, the men's chances of survival were dwindling.

It had been a slow acceptance of a grim reality, and yesterday was no different as the sorrowing relatives entered the large auditorium.

But within 10 minutes, a wail split the air: "Oh my God."

People stumbled out in tears, distraught, falling into each other's arms.

Sisters, grandmothers and strong, stocky fathers sobbed and supported one another as they returned to their cars.

A second explosion in the mine two hours earlier had crushed any hope. The 29 men were pronounced dead.

After days of not knowing, such abrupt certainty broke a community that had shown itself to be among the toughest.

In moments, hundreds of loving hearts were shattered.

Pike River Coal chief executive Peter Whittall broke the news to the gathering and crumbled in tears.

"It was absolute despair," said Grey District Mayor Tony Kokshoorn. "When the news came, everyone just cracked up."

The community would never be the same, he said. "There's some distraught people, I tell you. It's unbelievable.

"This is the West Coast's darkest hour ... It doesn't get worse than this."

Laurie Drew, father of one of the lost miners, held his anger in check as he spoke out after the briefing.

But there had been immediate abuse hurled around the hall, he said. Why had the rescue operation failed them?

"They're all dead. I don't know what to say. They're all dead.

"I'm a father. I want my son back."

The meeting was supposed to deliver hope. A bore hole to measure gas levels deep in the mine had been punched through yesterday morning. Robots had been sent in to investigate.

Finally, after waiting so long, a clearer picture of conditions in the mine was supposed to end the suffocating uncertainty.

Mr Whittall faced the crowd eager for good news, and eyes lit up. Applause broke out.

"I was hoping to turn up to tell them we were going into the pit," Mr Whittall told TVNZ's Close Up last night.

"I had gone in with the hope of being able to tell them we had started the rescue operation."

But the glimmer of hope only made the bad news harder to accept.

A mother collapsed on grass outside the building and sat stunned for 45 minutes.

A young woman was carried to an ambulance to recuperate.

Friends rushed in with cars to help the abruptly bereaved to get back home.

It was two hours before the last person left the building and its surroundings.

Superintendent Gary Knowles, who had led the planning for a rescue, said the second explosion had been so severe that the rescue team had immediately agreed that all hope was lost.

"The blast was prolific, just as severe as the first blast," the police commander said.

"Based on that explosion, no one would have survived ... We are now going into recovery mode."

In every other announcement he made, Mr Knowles had been careful not to use the word "recovery" - implying the miners were dead - instead repeating day after day that he was leading a rescue operation.

Yesterday afternoon, that shield, too, was punctured.

Prime Minister John Key said New Zealand had become a nation in mourning.

"New Zealand is a small country, a country where we are all our brother's keeper. To lose this many brothers at once strikes an agonising blow."

The All Blacks will wear white armbands when they play Wales this weekend and will keep a minute's silence before the game.

Coach Steve Hansen said the thoughts and prayers of all the players were with those who had lost loved ones.

"We are helpless here on such a sad day ..."

Hansen said everyone in the All Blacks party was acutely aware of the situation because of NZ Rugby Union president John Sturgeon, who is travelling with the team.

"He is a West Coaster," Hansen said, "and he is a miner."