British Islamic State leader Mohammed Emwazi, who was known as ‘Jihadi John,’ was targeted in a U.S. airstrike in northern Syria on Nov. 13. British Prime Minister David Cameron said his death could not be confirmed, while the Pentagon said it was still assessing the the strike’s effectiveness.

The militant, who is known for appearing in videos dressed entirely in black with a balaclava covering all but his eyes and the bridge of his nose, became a symbol of Islamic State brutality.

Emwazi appeared in videos showing the murders of U.S. and Japaenese journalists Steven Sotloff, James Foley, and Kenji Goto, as well as American and British aid workers Abdul-Rahman Kassig, David Haines, and Alan Henning.

Britain stated his death would “strike at the heart of Islamic State.”