Six weeks ago, a photo that will likely go down as one of the Syrian war’s iconic images went viral. It showed the corpses of men in a dried-out river, their hands bound behind their backs, and gunshot wounds in the back of their heads. Now an investigation by The Guardian reveals the story behind the photo—and the 110 men who were massacred before it was taken. The victims were all male and of working age, and all had vanished either in regime areas or on their way to reach regime areas. It is believed that the men were executed in a park about four kilometers upstream from where the bodies were found and the photo taken. Though Syrian officials claimed a terrorist group was behind the massacre, nobody The Guardian interviewed believes that is true.