All around the world, people were united in grief and shock as a fire engulfed the historic Notre Dame Cathedral in the heart of Paris, with billowing smoke seen from miles away from the French capital’s centre.

Hundreds gathered outside the cathedral, many in tears, as flames tore through the beloved building, causing the roof to collapse. French President Emmanuel Macron cancelled a scheduled speech Monday to deal with the ongoing fire.

“Our Lady of Paris is in flames,” Macron said on Twitter. “Emotion for the whole nation. A thought for all Catholics and for all French. Like all our countrymen, I’m sad tonight to see this part of us burn.”

Nicolas Marang, 47, has lived in Paris for more than 25 years and took video as Notre Dame’s spire collapsed amid the raging fire. He told NBC News he was running along the Seine River when he saw the smoke, which looked like a “dark smog,” coming from the Notre Dame.

The scene outside the cathedral was “confusing and devastating,” according to Marang.

“Something just collapsed inside me,” he said.

” One of the worst things I’ve ever seen.”

David Kang, 38, said he was on his way home when he passed by the Notre Dame and noticed the flames. People stopped all around, in shock, as they witnessed the landmark’s destruction.

“It was an emotional experience. I see it every day on my way to home, it was so sad,” Kang said.

“I don’t remember something like this ever happening. Notre Dame is the centre of Paris.”

Audrey Edwards, 71, an American who retired to Paris in 2017, said she saw the smoke from her apartment window.

“I’m not a particularly religious person. Notre Dame is a masterpiece architecturally, and as a real estate broker, I started to tear up because it’s such a magnificent structure, aesthetically speaking,” she said.

Edwards lived in Brooklyn and related the experience of seeing the plumes of smoke Monday to the images of the Twin Towers collapsing in lower Manhattan on 9/11.

“These are the things that you think are going to be eternal, but of course, nothing is,” she said.

University of Michigan student Madeline Boersma is living in Paris while she studies abroad at Sciences Po. Boersma, 20, said she was headed home from class but circled back to see the fire.

“Just walking down the street, you see it all the time,” Boersma said.

“As I was walking up here I thought, ‘I was just walking here three weeks ago and it was so normal.’ Today I’m here and everyone is heartbroken.”

Gabriella Pilet, an Argentinean who has lived in Paris for 20 years, stood near the Seine and sang the Hail Mary prayer in French as the cathedral burned.

“I came here to honour this place,” Pilet said.

“For me, it’s a symbol of gathering. Everyone, even if you’re not a Christian, comes here to gather.”

Pilet said she regrets never going up to the roof of the church as she had always planned.

“All the way at the end that was my favourite thing, a statue of the Virgin Mary,” Pilet said.

“Several years ago after the terrorist attacks, they stopped you from visiting some places. I was very upset.”

President Donald Trump called the Notre Dame one of the “great treasures of the world” during an economic roundtable event in Minnesota.

The cathedral is “beyond countries, that’s beyond anything, that’s part of our growing up, it’s a part of our culture, it’s a part of our lives,” Trump said.