France is in shock after two Islamic State followers slit the throat of an elderly priest during an attack on a church in northern France.
Here's everything we know so far.
Two men, armed with knives, stormed into a church in Saint-Etienne-du-Rouvray and took priest Father Jacques Hamel and four others hostage.
A nun who managed to escape said the attackers forced the 85-year-old priest to kneel, before killing him and filming themselves preaching in Arabic.
Officers shot dead the attackers - one of whom was wearing an explosive belt - as they emerged from the church.
One of the hostages is still fighting for her life.
Who were the attackers?
One of the attackers has been identified as 19-year-old Adel Kermiche, who was arrested after making an attempt to reach war-torn Syria last year.
Kermiche was well-known to French intelligence services and was under close surveillance.
The teenager - who was from the same Normandy town where the attack took place - was released from prison in March and forced to wear an electronic tag.
The other knifeman has been identified as Abdel Malik P., according to a judicial source.
They said the delay in identifying the 19-year-old was caused by ongoing DNA tests.
His identity card was allegedly found at the home of the other assailant, Adel Kermiche.
Police confirmed one person has been arrested in connection with the attack and raids are underway for any accomplices.
Is this another IS-inspired attack?
It appears so.
A day after the church attack, a video emerged via the Amaq news agency - the media wing of the so-called Islamic State - showing the two church attackers.
Francois Hollande, visiting the scene of the attack, said the attack was carried out by “two terrorists who claimed to be from Isis” and the terror group confirmed two of its "soldiers" were responsible.
Both attackers were known to intelligence services after trying to travel to Syria.
What have witnesses said?
Sister Danielle managed to escape from the church after the attackers had asked the priest to kneel.
"They forced him to his knees. He wanted to defend himself. And that's when the tragedy happened.
"They recorded themselves. They did a sort of sermon around the altar, in Arabic. It's a horror."
Claude-Albert Seguin lives near the church and said he heard gunshots for 30 seconds after police responded to the emergency call.
He added that he knew the priest who was murdered: "Everyone knew him very well. He was very loved in the community and a kind man."
How has the world reacted?
Francois Hollande described the attack as an "an ignoble terrorist attack”, saying IS had "declared war on us".
Prime Minister Theresa May said the attack was "sickening", adding: "The terrorists will not win."
Pope Francis condemned the "pain and horror of this absurd violence".
The Archbishop of Canterbury, Justin Welby, took to Twitter to express his sorrow: "Evil attacks the weakest, denies truth and love, is defeated through Jesus Christ. Pray for France, for victims, for their communities."
French Prime Minister Manuel Valls called the attack “barbaric”, saying it was a blow to the Catholic community and the whole of France.
"We will stand together,” Valls tweeted.
Another terrorist atrocity
The incident comes at a time when France remains on high alert following a spate of terrorist atrocities in the country, the most recent leaving 84 people dead in Nice.
Two recent IS-inspired attacks in Germany have also heightened terrorism fears in Europe.
Questions will need to be asked of the French authorities after the attack, according to our Security Editor Rohit Kachroo.
"This isn't a new normality to them [France] as it is in Germany. It's 18 months since the Charlie Hebdo attacks, and they've had a long time to confront these problems."
But he added that "no country in Europe has yet to find a solution."