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The man killed by Boston officers he had threatened with a knife represents the kind of homegrown extremist that a federal pilot program seeks to counter, if what authorities allege is true — and for some, raises doubts of whether the preventative measures are being communicated or can ever even work.

The FBI and Boston police say their joint terrorism task force had been monitoring Usaama Rahim for some time — though they have declined to say exactly how long — and had placed him under 24-hour surveillance when they intercepted messages suggesting he imminently planned to attack police. Rahim was fatally shot June 2 in a drugstore parking lot after, authorities say, he lunged at six task force members with a military-style knife as they sought to question him.

Glenn Katon, legal director for the California-based Muslim Advocates and a critic of the federal pilot program called Countering Violent Extremism, suggests authorities may have missed an opportunity with Rahim.

"This begs the question of whether CVE is ever going to work, under any circumstance," he said. "I'm really, really skeptical."

Under Countering Violent Extremism, launched to fanfare by the Obama administration in February after months of development, law enforcement and Islamic and community leaders are supposed work together to tackle terrorism by preventing radicalization from taking root among youths and others vulnerable to extremist propaganda like that spread online by the Islamic State group.

The initiatives, which are also being tested in Los Angeles and Minneapolis and will be rolled out nationwide if deemed effective, take many forms, including town hall discussions, educational and training programs, mentorships, and social media campaigns.

Local law enforcement officials in various cities have been doing similar outreach for years — Boston's efforts alone stretch back about a decade — but now that it's been formalized as a federal program that could be replicated nationwide, some Muslims and others fear the efforts could compromise civil liberties and religious freedoms and amount to disguised intelligence-gathering.

Robert Trestan, who has helped develop Boston's Countering Violent Extremism program as New England director for the Anti-Defamation League, said it's unfair to connect Rahim's shooting with the federal efforts.

"The real test would have been if the CVE program had been in place two years ago, when the first indicators were raised that this person might pose a danger," Trestan said. "All the information we have right now indicates that at the time (authorities) were going to speak to him, he was already down that path."

Authorities have said little about how Rahim, a 26-year-old black Muslim, caught their attention other than to say he and his nephew, David Wright, had plotted to commit some kind of attack, and that Rahim ordered three large knives on Amazon.com a week earlier.

Wright, 25, of Everett, Massachusetts, and another man, Nicholas Rovinski, 24, of Warwick, Rhode Island, have since been charged with conspiring to help the Islamic State group by plotting with Rahim.

The FBI and Boston police declined to comment for this article, as did the office of Massachusetts U.S. Attorney Carmen Ortiz, which is coordinating the anti-extremism effort in Boston.

The Rahim family has said revelations about his radicalization have come as a "complete shock."

Imam Abdullah Faaruuq, head of the Mosque for the Praising of Allah, where Rahim and his family often prayed, said he wasn't even aware of Countering Violent Extremism, raising questions about how well authorities have communicated about the program, in which religious leaders are supposed to be integral.

He believes he or others could have intervened if authorities had informed the mosque early on about what they knew of Rahim's extremist views.

"I wish I was aware," he said of the federal anti-extremism program. "I'm very hurt and disappointed that we could not have played a more prominent role to rein him in."

Shannon Erwin, co-founder of the Boston-based Muslim Justice League and a critic of Countering Violent Extremism, cautioned that it's early to speculate about whether authorities were right to monitor Rahim in the first place.

"We don't even know if any of the allegations against him are true," she said. "I don't think we can accept that yet, even though it has been a law enforcement narrative."

Local authorities shared a grainy surveillance video capturing much of the June 2 shooting, though Rahim's family, civil rights groups, and some black and Muslim leaders say the video is not conclusive and raises questions of whether police acted responsibly.

The Rahim family has called on U.S. Attorney General Loretta Lynch to intercede; they maintain authorities tried to illegally arrest Rahim without a warrant, leading to his death.

Faaruuq, Katon and Erwin's groups, meanwhile, are among 10 organizations, including the American Civil Liberties Union and the Council on American-Islamic Relations, that have asked the office of state Attorney General Maura Healey to investigate the shooting this week.

The Suffolk County district attorney's office and the FBI are conducting separate inquiries.