In an interview two days later with Katie Couric, Foley's younger brother, Michael, recounted how Pope Francis had called the family to console them and in their conversation "referred to Jim's act as, really, martyrdom."
Numerous commentators had already picked up on that idea, holding up Foley not only as a witness to the Christian faith but also as a spur for believers in the West to take more seriously the plight of Christians in Iraq and elsewhere in the Middle East who are being persecuted to a degree that some say is comparable to genocide.
But in the Catholic Church, determining whether someone is a martyr is not so easy. Historically, two conditions must be met.
First, even if martyrs weren't saintly or pious Christians throughout their lives, there should be evidence that they held fast to their faith in their final moments and that this witness can serve as an example to others.
Foley certainly seemed to take solace in his faith under duress.
In a 2011 essay he wrote for the alumni magazine of Marquette University, his Jesuit-run alma mater, Foley spoke movingly of his belief in prayer, and especially his recourse to the rosary to sustain him when he was imprisoned in Libya earlier that year while covering the downfall of Moammar Gadhafi.
That was also the heart of a message that Foley managed to send from his captivity at the hands of the Islamic State; after the episode in Libya, Foley, a photojournalist, went to cover the civil war in Syria and was kidnapped there on Thanksgiving in 2012. He was held with as many as 17 other prisoners and had a fellow captive, who was later released, commit to memory a letter in which Foley spoke of how prayer and faith kept him close to his family.
"I feel you all especially when I pray," Foley said. "I pray for you to stay strong and to believe. I really feel I can touch you even in this darkness when I pray."
The second factor in determining whether someone is a martyr is that they must be killed explicitly because they are a Christian, or "in odium fidei," out of hatred for the faith. That's where martyrdom arguments can get complicated — and messy.
For example, Salvadoran Archbishop Oscar Romero, who lived under constant threat for his advocacy on behalf of the poor and in defense of human rights, was immediately hailed as a martyr in 1980, when he was assassinated by paramilitary forces while celebrating Mass.
But under the papacies of John Paul II and Benedict XVI, Romero's canonization cause was repeatedly stalled because conservatives in the Vatican argued that Romero had become an icon of liberation theology and was killed for political rather than religious reasons.
Only this month, in fact, Pope Francis — who has long revered Romero – announced that the archbishop's sainthood process had been "unblocked."
Francis also indicated that he wanted the church to consider whether those who are killed "for performing the works that Jesus commands us to do for our neighbor" are martyrs just as those who are killed for professing the creed. If that happens, it could mark a significant shift in the church's understanding of martyrdom.
Yet some also worry that Foley is being promoted as a martyr in part because he can serve as a Christian rallying cry against extremist Islam, or as a way of building momentum for a more forceful Western intervention in Iraq.
So the question then comes down to parsing the rationale of Foley's killers: Did they murder him because he was a Christian or because he was an American? Did they kill him because he would not convert, or did they kill him to provoke the West? Was he a martyr for the faith or, as Foley's father added, "a martyr for freedom"?