What's the most logical way to complete this passage?

Islamic State terrorists have released a horrific new video showing the execution of a prisoner killed with a pump-action shotgun. This latest graphic and shocking footage has all the militants' trademark slick production effects and features a light-skinned executioner dressed in similar costume to the now infamous 'Jihadi John'. The prisoner, believed to be a Syrian soldier captured by ISIS, is forced to wear the same kind of orange jumpsuit worn by Western hostages before they are savagely beheaded by the terror group. The killer is seen ranting in Arabic behind the doomed prisoner before the HD footage is edited into slow-motion and the militant is seen catching the shotgun, thrown to him by somebody off camera.

Killer: When he finally finishes ranting the
ISIS executioner raises the shotgun and fires a single round into the back of the man's head, causing him to slump forwards, face-down in the dirt