A 78-year-old man with extreme right-wing views has killed himself in Notre Dame in Paris.
Dominique Venner shot himself beside the main altar of the cathedral in the French capital on Tuesday.
Mr Venner, a far-right historian, had recently been involved in the campaign against the government's decision to legalise gay marriage, the BBC reports.
On Saturday, President Francois Hollande signed the bill into law.
Police said Mr Venner had made no statement before killing himself, although a note was found next to his body. They did not disclose its contents.
Earlier on Tuesday, he had written on his blog a damning critique of the same-sex marriage bill.
"New spectacular and symbolic actions are needed to wake up the sleep walkers and shake the anaesthetised consciousness," he wrote. "We are entering a time when acts must follow words."
Mr Venner was also a former member of the Secret Army Organisation (OAS), which opposed Algerian independence in the early 1960s and tried to assassinate Charles De Gaulle.
Police said the cathedral was evacuated immediately following the shooting, that there were no further problems, and that the church for the moment remained closed.
The rector of Notre-Dame, Monsignor Patrick Jacquin, said the shocking death was the first suicide in decades at the cathedral.