IS executioner Mohammed Emwazi, known as Jihadi John.

The masked “Jihadi John” killer who fronted “Islamic State” beheading videos has been identified as Mohammed Emwazi, a British computer programming graduate from a well-to-do London family.

The black-clad militant brandishing a knife and speaking with an English accent was shown in videos released by “Islamic State” (IS) apparently decapitating hostages, including Americans, Britons and Syrians.

The 26-year-old militant used the videos to threaten the West, admonish its Arab allies and taunt President Obama and British Prime Minister David Cameron before petrified hostages cowering in orange jump suits.

Emwazi’s name was first disclosed by the Washington Post, citing unidentified former associates, but two U.S. government sources who spoke on condition of anonymity confirmed to Reuters that investigators believed Jihadi John was Emwazi.

Dressed entirely in black, a balaclava covering all but his eyes and the bridge of his nose, and a holster under his left arm, Jihadi John became a menacing symbol of “Islamic State” brutality and one of the world’s most wanted men.

Hostages called him John as he and other Britons in “Islamic State” had been nicknamed “the Beatles.”

Emwazi was born in Kuwait but came to Britain at age 6 and graduated with a computer programming degree from the University of Westminster before coming to the attention of Britain’s main domestic intelligence service, MI5.

An associate of Emwazi, who was a fluent Arabic speaker, said MI5 tried to recruit him and then prevented him from traveling abroad, forcing him to flee abroad without telling his family. He traveled to Syria around 2012.

MI5 does not publicly comment on such claims. The British government and police refused to confirm or deny his identity, citing an ongoing security investigation.