French-American François-Xavier Lochet, 70, was attending Mass at Notre Dame Cathedral on Monday when a loud alarm went off just as the congregation began the Universal Prayer -- it was so loud Lochet could barely understand the messages in French and English.

Most of those who heard it, however, just stood there as visitors began to be ushered out of the cathedral. That was until, Lochet said, a police officer approached a priest and told him, "This is no joke. You've got to get out."

Lochet began walking back to his mother's home when he turned around and saw smoke.

"Nobody was paying attention," he said. "I stopped and I took my phone out and I waited."

Soon, smoke began billowing out from the cathedral.

"To me. I felt like crying," he said. "This is my most favorite church probably in the world. To me, as a kid, I climbed the towers when I was 12 years old."

He could not help but think about the countless craftsmen who devoted their entire lives to constructing the church, even those who helped renovate it. He'd often go to Mass, or just to listen to the cathedral's organs.

"It's a huge piece of history of Europe," he said. "Gone."

He took this photo of the early flames. That spire, and much of the roof on which it sat, would later fall: