A statement from Scotland Yard also said it would not confirm the identity of the man, identified by The Washington Post as Mohammed Emwazi. (AFP/Getty Images)

To some, he was slightly shy computer programming student who liked to keep up on fashion trends. In the view of at least one acquaintance, he was apparently pushed toward Islamist militancy by repeated pressure from British authorities.

And for Britain’s counterterrorism experts, he represented the focus of an intense forensic analysis to seek the identity of the Islamic State’s English-speaking “Jihadi John.”

These multiple impressions intersected Thursday in a range of anger, dismay and angst after The Washington Post revealed his identify as Kuwait-born Mohammed Emwazi.

“If these allegations are true, we are shocked and sickened by the news,” said a statement from the University of Westminster, where Emwazi studied. “Our thoughts are with the victims and their families.”

Britain’s counterterrorism chief said authorities will not disclose details of its investigations into “Jihadi John.” The Scotland Yard statement also said it would not confirm the identity of the man.

Scores of hostages, including Westerners, have been killed by the Islamic State since 2014.

But that did not stop a wave of reaction and commentary, including alarm over the extent of the Islamic State’s outreach to the West and questions about the measures taken by authorities against suspected threats.

A London-based rights group — cited in the Post story — claimed that tough anti-terrorism measures in the West and tactics such as ethnic profiling would likely push more young Muslims and others to become radicalized.

“This case should trigger thinking about British domestic and foreign policy,” said Asim Qureshi, research director for CAGE, a group that monitors international counterterrorism measures.

[Read: Islamic State killer is identified as Londoner Mohammed Emwazi]

The Post report said Emwazi — who has appeared in Islamic State videos issuing proclamations and carrying out several beheadings — is believed to have traveled to Syria around 2012 and later joined the Islamic State.

The Post said counterterrorism officials in Britain detained Emwazi in 2010, fingerprinted him and searched his belongings.

Shortly after the story broke, reporters descended on the West London home where Emwazi grew up — a brick row house in a well-to-do area with pockets of deprivation. One neighbor popped his head out the door and shouted expletives at the gathering of about 40 journalists. None of the other neighbors answered their doors. It was not immediately clear whether any of Emwazi’s relatives currently live at the address.

The identity of the masked man whose video appearances have come to symbolize the barbarity of the Islamic State has been made public. (The Washington Post)

Worshipers at a mosque about 100 yards away expressed shock that the man known as Jihadi John once lived around the corner.

Khosru Khan, 32, a travel agent who was praying at the Harrow Road Jamme Mosque, said: “It’s a big shock to me and everyone here. . . . The Muslim community has been demonized here and around the world. He seems to be some sort of bogeyman for the Muslim community. We don’t know who he is.”

Cmdr. Richard Walton, head of the Metropolitan Police’s Counter Terrorism Command, said no public details of the ongoing probe into Emwazi will be released.

[View: The atrocities of the Islamic State]

“We are not going to confirm the identity of anyone at this stage or give an update on the progress of this live counterterrorism investigation,” Walton said in a statement.

In Washington, a senior White House adviser, David Simas, said the disclosure underscores the need “to build on the work” of a 60-nation conference hosted by President Obama on combating violent extremism.

Simas, director of the Office of Political Strategy and Outreach, told CNN that the Islamic State’s extensive recruitment efforts pose a “new, evolving threat.”

But analysts cast doubt on the idea that measures by British authorities, including the domestic intelligence agency MI5, had triggered Emwazi’s radicalization. They noted that his story about traveling to Tanzania to go on safari was likely a ruse to obscure plans to link up with militants in Somalia.

“It doesn’t ring true,” said Nick Lowles, chief executive of the anti-extremism group Hope Not Hate. “It’s a bit like the jihadis who say they’re going on a package tour to Turkey, then once they’re there, shoot over the border to Syria.”

The International Center for the Study of Radicalization, a leading authority on foreign recruitment methods by militant groups, described the Post’s reporting on Emwazi’s identity as “accurate and correct.”

[Read: Emwazi filed a complaint with police. This is the response.]

“The fact that ‘Jihadi John’ has been unveiled in this manner demonstrates that whatever efforts are made, the ability to mask one’s identity is limited or in fact impossible, and their true identities will eventually be revealed,” said a statement from the center, which is based at King’s College in London.

“This demonstrates what we have long said about radicalization, that it is not something driven by poverty or social deprivation,” the center added. “Ideology clearly plays a big role in motivating some men to participate in jihadist causes.”

The daughter of British aid worker David Haines, who was beheaded in September by Jihadi John, told ITV News that identifying the masked man was “a good step,” the Associated Press reported.

“But I think all the families will feel closure and relief once there’s a bullet between his eyes,” Bethany Haines said.

The family of American journalist Steven Sotloff, who was similarly murdered earlier that month, expressed hope that the killer would go to prison. The family said it felt “relieved” and took “comfort” from the disclosure of Emwazi’s identity, according to the BBC.

“We want to sit in a courtroom, watch him sentenced and see him sent to a super-max prison where he will spend the rest of his life in isolation,” the BBC quoted a family spokesman as saying.

Earlier this month, the director of the U.S. National Counter Terrorism Center told a congressional panel that an estimated 20,000 foreigners from 90 countries — including about 3,400 from Western nations — have joined militant factions in Syria, including the Islamic State.

Worries about Islamic State recruitment are particularly acute in Europe, where authorities have increased surveillance for citizens seeking to reach Syria or returning home after contact with the militants.

Last month — just days after a series of terrorist attacks rocked Paris — police in Belgium and other countries conducted raids against suspected cells linked to Islamic State sympathizers.

In New York, three men — all born in Central Asia — were arrested on Wednesday on charges of plotting to join the Islamic State.

Murphy reported from Washington.