His earlier, innocent image can be seen in video obtained from Britain's Channel 4.
It shows a teenage boy in the schoolyard of a West London secondary school. He walks through a sea of fellow students in his zippered sweatshirt over his polo shirt, wearing a backpack and carrying a plastic bottle. At one point, a basketball rolls toward him and he returns it with a deft kick.
He looks playful at times as when he skips and lightheartedly pushes two other boys, more serious in others.
In other words, he appears to be not much different than any other teenager.
But he's not. The boy in the video is Emwazi, his former headmaster at Quintin Kynaston Community Academy told CNN.
Who Mohammed Emwazi used to be
Jo Shuter noted that her former student could be shy at times, but overall he was far from a troublemaker and not much out of the ordinary.
"He was bullied a little bit, because he was quiet and reserved," Shuter said. "Generally, he was fine. There (were) no issues with him. There were no problems."
Emwazi became even more focused in his last few years at Quintin Kynaston Community Academy, she said.
"He was working hard, he achieved great grades for him, and he went to the university of his choice," Shuter told CNN this week, referring to London's Westminster University, from which Emwazi graduated in 2009.
Contrast that perception with that of the masked, deep-voiced, British-accented man who months ago was dubbed Jihadi John.
There is nothing shy, nothing gentle, nothing playful about him. He starred in grisly ISIS videos depicting the beheading of hostages, punctuating his horrific actions with taunts at the United States.
A man who says he is Emwazi's father told the Kuwaiti newspaper al Qabas that "there is nothing that proves" the man known as Jihadi John is his son, Mohammed. His Kuwait-based lawyer, Salem Al-Hashash, told CNN that the family plans to sue anyone who makes the connection, calling the father Jassem Emwazi a "victim of libel."
Yet Western authorities have made just such a link.
They say that the Kuwaiti-born Mohammed Emwazi went from being a typical "boy next door" type growing up in West London to being one of the most high-profile recruits of ISIS, the Islamist extremist group behind a campaign of terror and conquest in Syria and Iraq.
More than a dozen British administrative court documents obtained by CNN indicate that, as far back as 2009, British security services believed Emwazi was part of a radical West London recruitment network for terrorist groups in East Africa.
And in late February, two U.S. officials and two U.S. congressional sources confirmed reports in British and other media that Emwazi went on to join ISIS and is the man known as Jihadi John.