CNN:

His voice became hauntingly familiar as the masked man with a British accent who appeared repeatedly in brutal beheading videos from ISIS.

But the identity of "Jihadi John" remained a mystery -- until Thursday, when two U.S. officials and two U.S. congressional sources confirmed it.

The man, the officials said, is Mohammed Emwazi, a Kuwaiti-born Londoner.

The officials, who've been briefed on the matter, spoke to CNN after a Washington Post report first revealed Emwazi's identity.

Emwazi is believed to have traveled to Syria in 2012, according to the newspaper, and later to have joined ISIS there.

Even with a name and face for the man behind the mask, uncertainty still swirled Thursday. London police and British officials declined to confirm his identity. Officials from a London-based human rights and Muslim advocacy organization who've interacted with Emwazi said they couldn't be 100% certain it was him.