BEIRUT (AP) — Islamic State extremists released a video showing the beheading of British aid worker David Haines, who was abducted in Syria last year, and British Prime Minister David Cameron late Saturday condemned his slaying as “an act of pure evil.”

Cameron confirmed Haines’ death in a statement after the British Foreign Office had said earlier that it was “working urgently to verify the video.” Haines is the third Westerner beheaded in recent weeks by the Islamic State group, which has seized vast swaths of territory in Syria and Iraq.