What to know:
The man believed to be the ISIS terrorist dubbed "Jihadi John" has been identified as a British man named Mohammed Emwazi.
Emwazi was was born in 1988, making him 26 or 27 years old, the BBC reported.
An activist group he communicated with before allegedly going to Syria said that Emwazi was born in Kuwait but moved to England when he was 6 years old.
Emwazi's family lives in Queens Park, a neighborhood in North West London.
The neighborhood is considered to be working class.
Neighbors told ABC News that Emwazi's relatives have not been seen at their home in the past week.
He attended high school at Quintin Kynaston Community Academy in the St. John's Wood neighborhood of North London, the BBC reported.
The University of Westminster confirmed to ABC News that a student by the same name left the school in 2009.
"If these allegations are true, we are shocked and sickened by the news," a spokesman for the university said in a statement.
Matt Olsen, former director of the National Counterterrorism Center and current ABC News consultant, said Emwazi's background points to a disturbing wrinkle.
"The identification of this individual, if it turns out that it is in fact confirmed, really just underscores the concern that ISIS has the ability to reach into London and recruit somebody who's well-educated and comes from a middle-class family," he said. "That's a real concern for everyone in the counter-terrorism community."
In 2010, Emwazi reportedly attempted to move to Kuwait but was stopped from doing so by British counter-terrorism officials, according to activist group CAGE.
Qureshi described Emwazi as a "beautiful young man" when they met in the summer of 2009 to discuss Emwazi’s complaints about being detained and harassed by British authorities as he traveled.
He said he cannot confirm that the man in the "Jihadi John" video is Emwazi because his face is covered, but added that the personality is very different from the one he knew in London. He described Emwazi as kind, gentle and soft spoken.
He said Emwazi told him he didn't "want to live in a country where I’m treated as the enemy."
"What happened to him after then? I can’t tell you. I don’t know myself," Qureshi said.
"Jihadi John" gained international attention in August 2014 when he appeared to be the masked man who executed American journalist James Foley in a video that became the first in a disturbing string of similar executions.
He spoke English with a British accent in the video, hence his nickname, "Jihadi John."
Neither British nor American government officials have publicly confirmed the masked man's identity, but both have expressed concerns about how this revelation could impact ongoing investigations.
President Obama declined to comment on "Jihadi John" while speaking to ABC affiliate KOMO-TV in Seattle, but vowed again to bring those who harmed Americans to justice.
A spokesman for the family of Steven Sotloff, an American whose execution allegedly took place at the hands of Jihadi John, is now calling for Emwazi to be brought to justice in America.
“The Sotloff family was confident law enforcement would find him out and bring him to justice and they have full confidence the U.S. government will be able to do that,” the statement said. “The family would like to see him brought to a court in N.Y. or eastern Va. and watch him prosecuted for the beheading of their son and convicted to life in a super max facility. This is how justice is served in this country.”
Bethany Haines, the daughter of British hostage David Haines, who was purportedly killed in one of the ISIS videos, told Britain’s ITV that identifying “Jihadi John” was a good step but only the first.
"I think all the families will feel closure and relief once there’s a bullet between his eyes," she told ITV.