Johann Vexo was playing at a service when the fire broke out. The priest stopped the service and told the congregation to evacuate the 12th century cathedral.
He said he was startled when the alarm sounded on Monday in the middle of Mass.
"It was the first time for everyone, we've never heard this fire alarm before," he claimed.
"There was an alarm and then some messages in French and in English asking people to leave the cathedral."
After leaving the building Mr Vexo initially went home. But seeing smoke across the skyline of Paris, and flames spreading across the Gothic cathedral's roof, he tried to go back to the church.
"I went back, not to Notre Dame because it was impossible to go very close, so I stayed maybe four hundred metres from the cathedral," he said.
"I saw the fire in the framework and on the roof.
"My colleagues feel the same, of course. It's absolutely terrible."
The fire happened during the most holy week of the year for Christians. Mr Vexo recognises that adds to its poignancy.
"I don't know what will happen about the services we were supposed to have in Notre Dame. But it's the most busy week of the year - Holy Week. So it's especially hard during this time."
Mr Vexo has not yet been able to go back into the charred remains of the building.
He told Premier he's keen to find out whether the flames and smoke have done irreparable damage to the three organs used for services at Notre Dame.
In the longer term he hopes experts will manage to restore the building as near as possible to its condition before the fire broke out.
He added: "I think everyone wants to see Notre Dame again exactly as it was before. I don't know if it's technically possible or not.
"But I think all the people who worked at the cathedral or lived nearby just want to see the cathedral exactly the same."
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