But many of those who grew up with him have told the UK media that remember Emwazi altogether differently: as the typical "boy next door," a popular kid who loved football, pop music and The Simpsons.
A day after the long-standing mystery behind Jihadi John's identity was solved, clues to his past have begun to emerge -- but far from showing him as a violent extremist, they paint a picture of an ordinary child and teenager growing up in the British capital.
Emwazi was born in Kuwait in 1988, and moved to the UK with his parents, Jasem and Ghaneya, and sister at the age of six, according to CAGE, an advocacy group for those affected by terrorism investigations
The family settled down in west London; Emwazi's father is reported to have worked as a taxi driver, while his mother stayed at home
to look after Emwazi and his siblings.
He is reported to have attended St Mary Magdalene Church of England Primary School
, in London's Maida Vale; a photograph published on the front pages of several British newspapers showed a smiling young boy in the school's scarlet sweater uniform, surrounded by his classmates and teacher -- a far cry from the black-clad jihadi infamous around the world.
When contacted by CNN, the school's headteacher refused to comment. On its website
, the school -- whose motto is "believe, achieve and succeed together" -- proudly proclaims: "We are a very inclusive, multicultural and diverse school, where many languages and religions reside happily under one roof."
A former classmate there told the Daily Mail newspaper
that Emwazi was sporty and popular, but had initially struggled with English: "He could only say a few words at first, like his name and where he was from.
"He played football every lunchtime and at the after-school football club. Through football, he learned different words and expressions."
The paper reported that, writing in a class yearbook aged 10, Emwazi told of his love for pop group S Club 7, The Simpsons, the shoot-'em-up computer game Duke Nukem and -- like so many other British children -- listed his favourite food as chips.
Another friend from St Mary Magdalene told radio station LBC
: "I used to go with him to that primary school ... I do remember him very well ... I was a year younger than him and he treated me as someone he used to teach."
The man, who was identified only as Mohammed, said the pair's mothers had been "very good friends" until three years ago when rumors began to circulate about Emwazi's terror links. "His mum used to sell gold and stuff like that to the local community."
Mohammed and another former classmate both said they have vivid memories of a painful injury sustained by the youngster when he was in the final year of primary school.
"In the playground ... He was just about to get into a fight and he was running away from someone ... another guy tried to block off his path. He had nowhere to go and he basically ran into the goalposts, hit his head onto a metal goalpost and fell to the floor," Mohammed told LBC, adding that his friend missed two weeks of classes and "he was not the same, ever since that brain injury."
Londoner Matt Seton wrote on Twitter that he went to school with Emwazi
: "He was a 12 year old kid ... I remember one [time] we were playing football and he smashed his head on the goalpost. Now he kills people for a living."
After leaving St Mary Magdalene, Emwazi is believed to have moved on to the Quintin Kynaston Academy
in neighboring St. John's Wood, whose alumni include singers Tulisa Contostavolos and Shola Ama; his sister later became a prefect
One of his classmates -- speaking on condition of anonymity -- told the Daily Telegraph newspaper he was a "typical north-west London boy."
"He seemed like a nice guy ... a down-to-earth person and humble. He liked football and he was friends with everyone. All the Indian boys, all the Pakistani boys, people from different religions, he spoke to everyone."
A former teacher told Britain's Channel 4 News that Emwazi was "a diligent hardworking lovely young man
. Responsible, polite, quiet. He was everything that you'd want a student to be.
"He was somebody who would always seek the correct way of handling something. He did things in the right way," she insisted. "There was never any indication of any violence at all."
The unidentified educator said her ex-pupil "was religious ... and I think as he got older he did become more devout. He would go to the mosque on Fridays and pray but a lot of our kids did that."
Asim Qureshi, research director of CAGE
, insists that the Mohammed Emwazi he knew was "very kind, extremely gentle, [a] humble individual
, who didn't have any self-importance about himself."
Intelligence services and terrorism experts are now piecing together just how he went from that to the infamous "bogeyman" of ISIS -- something which continues to puzzle many of those who knew him as a boy.