At the moment of execution the rebels grasped his throat. The young man put up a struggle. Three or four rebels pinned him down. The man tried to protect his throat with his hands, which were still tied together. He tried to resist but they were stronger than he was and they cut his throat. They raised his head into the air. People waved their guns and cheered

◼ ..I knew I had to document this, as I had the three previous beheadings I had photographed that day... - TIME

What follows is a harrowing series of photographs of Islamic militants publicly executing, by decapitation, a young Syrian in the town of Keferghan, near Aleppo, on August 31, 2013.

Because of the danger in reporting inside Syria, it was not possible to confirm the identity or political affiliation of the victim. Nor are we certain about the motivation of his killers. One eyewitness who lives in the area and was contacted by TIME a week after the beheadings said that the executioners were from ISIS, an Al-Qaeda franchise operating in Syria and Iraq.

TIME obtained the images exclusively from a photographer who was recently in Syria. This decapitation was the last of four executions he documented that day. TIME has agreed not to publish the photographer’s name, to protect him from repercussions when he returns to Syria.