Petitjean and Adel Kermiche, 19, butchered Rev. Jacques Hamel, 85, after forcing him to kneel at the altar inside a church in the Normandy town of Saint-Etienne-du-Rouvray.
They also forced another man to record the execution before stabbing the hostage, who survived.
The jihadists, both of Algerian origin, were shown pledging allegiance to ISIS leader Abu Bakr Al-Baghdadi in a video made before they stormed the church and held several hostages, including nuns they used as human shields.
They were shot to death by police as they emerged from the church yelling, “Allahu akbar!”
The pope has checked in on this, on the side of sanity, peace, and order.
Pope says Islam is not terrorism
Aboard the papal plane (AFP) - Pope Francis said Sunday that Islam could not be equated with terrorism and warned Europe was pushing its young into the hands of extremists.
"It's not true and it's not correct (to say) Islam is terrorism," he told journalists aboard the papal plane during the return journey from a trip to Poland.
"I don't think it is right to equate Islam with violence".
Francis defended his decision not to name Islam when condemning the brutal jihadist murder of a Catholic priest in France in the latest of a string of recent attacks in Europe claimed by the Islamic State (IS) group.
"In almost every religion there is always a small group of fundamentalists. We have them too."
"If I have to talk about Islamic violence I have to talk about Christian violence. Every day in the newspapers I see violence in Italy, someone kills his girlfriend, another kills his mother-in-law, and these are baptised Catholics."
The pontiff was speaking after Muslims attended Catholic mass in churches around France on Sunday in solidarity and sorrow following the murder of the priest, whose throat was slit at the altar of his church.