YouTube quickly pulled the footage, but it was embedded elsewhere, and screenshots flashed across Twitter. Supporters and members of IS quickly spread the images and defended them, posting pictures of abuses by US troops at Iraq's Abu Ghraib prison and citing religious precedent for decapitation.
Foley had covered the war in Libya before heading to Syria, where he contributed to news site GlobalPost, Agence France-Presse and other media outlets. But online, jihadists accused him of being a spy, or claimed he deserved to die simply for being an American non-Muslim. He was dressed in orange clothes in the video, as jihadists online pointed out, in a reference to the jumpsuits worn by Muslim detainees at the US Guantanamo Bay facility.
Twitter users online made it clear Foley's death and the video were intended to spread fear.
"IS execution of the American journalist was a deliberate strategy, by showing brutality to the world puts the fear in IS enemies," tweeted one self-described "extremist" under the name Abu Bakr al-Janabi. "It's meant to evoke fear, terror and hatred," he added, writing in English.