Four months before a radicalized Charlotte, North Carolina blogger named Samir Khan left the United States for Yemen to edit al Qaeda's official magazine, two FBI special agents looped in the Joint Special Operations Command (JSOC) liaison who worked at the bureau's counterterrorism division on an email.

One agent told the other that the JSOC liaison was a "trusted partner," according the June 10, 2009 email, which documented the FBI's years-long pursuit of Khan. "He can talk to the folks at [headquarters] and see if there is any interest in potential support…. If there is something they can help out on, then we can potentially set up a meeting."

After 9/11, the FBI and JSOC worked out an arrangement in which a JSOC officer is assigned to the FBI's counterterrorism division, and an FBI agent is assigned to JSOC.

The FBI's communication with JSOC about Khan — he was known to write incendiary blog posts about jihad, his desire to see an Islamic caliphate, and his hopes for the deaths of Americans — is significant. Khan and the radical preacher Anwar al-Awlaki, central figures in Al Qaeda in the Arabian Peninsula, were killed in a drone strike in Yemen in September 2011 in an operation jointly conducted by the CIA and JSOC. The Obama administration said Khan was not an intended target of the drone strike.

The email, the earliest communication to surface about the involvement of special operations in the FBI's investigation of Khan while he was still living in the US, was included in hundreds of pages of heavily redacted FBI files on Khan VICE News obtained in response to a Freedom of Information Act (FOIA) request. This is the sixth installment in our long-running series on the US blogger turned "global extremist." The FBI has identified tens of thousands of pages of records and has been releasing the files to VICE News on a rolling basis.

Martin Reardon, the senior vice president of the private security firm The Soufan Group who was formerly the chief of the FBI's Terrorist Screening Operations Center, told VICE News that the JSOC email "was likely in reference to assistance they might be able to provide [FBI] with the [Khan] case in Yemen."

"JSOC had a huge presence and a lot of assets on the ground there up until last year, so could have been in position to provide intel on Khan," Reardon said. "JSOC routinely assists the FBI with [counterterrorism] cases in conflict areas."

Another email exchange between FBI personnel two days prior to the JSOC email discussed a "joint operation" that had been in the works for at least two months that an FBI agent wanted to "push forward." But details about it were redacted.

Khan had been on the FBI's radar for more than three years by the time the FBI agent sent the email to the bureau's JSOC liaison. Previous FBI files turned over to VICE News showed that the bureau discussed an "end game" for Khan, the details of which were redacted. The email the FBI agent sent looping in JSOC underscores the bureau's growing concerns that Khan was not just a blogger who proclaimed loyalty to al Qaeda, but was possibly turning into a recruiter for the terrorist group.

Indeed, the FBI files identified Khan as both a "radicalizer and recruiter." One of the most significant documents in the latest cache include notes from an FBI interview of an African-American Muslim convert that took place on June 2, 2009 in Concord, North Carolina. The man told FBI agents that on Election Day 2008 he called 1-800-WHY-ISLAM and "did it," meaning he "officially" converted to Islam during the phone call. He was directed to attend the Charlotte mosque frequented by Khan, where Khan served as his mentor, plying him with Muslim literature and recordings of Muslim speakers "who spoke in English." The potential informant told FBI agents that Khan encouraged him to become involved in jihad.

But not "bombings," he made clear. Rather, "in the struggle to de-Americanize America," because Khan wanted "America to be under Islamic law."

"When asked if [he] thought Khan would take up arms, [he] replied, 'Yes and no,'" the FBI's notes of the interview said. "Mainly 'No,' because Khan was all talk." Discussions about weapons centered around AK-47s, the "weapon of choice for the mujahideen."

The potential informant told FBI agents he converted back to Christianity and stopped returning Khan's emails and calls.

A couple of weeks later, on June 26, 2009, the FBI submitted a report stating that the bureau had cultivated a new confidential informant who had "become acquainted with Samir Khan." The meeting culminated in the planning of a special operation, which the FBI scrubbed, except for a request for "street clothes appropriate for discreet surveillance, hand-held and/or vehicle mounted radio." The operations plan included a photograph of Khan.

At the time, Khan was weeks away from leaving the US for Yemen in October 2009, so the FBI appeared to be aware of his travel plans, an indication that the radical blogger did not just slip out of the US undetected.

The FBI seemed intent on working with a major new source it cultivated, one that would require "significant funding," to deal with Khan once he left the US.

"Can we get your blessing on this," an FBI agent wrote in an email outlining what appears to be a plan for dealing with Khan. Another FBI agent responded, saying it seemed "like a good plan."

Shortly after Khan settled in Yemen, he became one of the founding editors of the slick English-language Al Qaeda magazine Inspire, which featured articles such as "Make a Bomb in the Kitchen of Your Mom."

"After he left the US in 2009, the FBI was still very interested in getting him," Reardon said. "Had he not been killed in the drone strike with Awlaki in 2011, Khan would most likely have been indicted on material support charges, which given his involvement with Inspire, would have been a slam dunk case" for the government.

The FBI had reached out to legal attaches in other countries for details about Khan and anyone he had communicated with overseas. An FBI agent received "one short document" in German on July 15, 2009 that needed to be translated.

Reardon said it's "standard in FBI investigations" to ask legal attaches for "background information from their host country counterparts (law enforcement and intelligence services) on FBI subjects, particularly terrorism subjects ... I was assigned to the office in Riyadh from 2003-2005 and we received requests like that almost every day."

FBI agents remarked in one email that Khan was keeping them busy, and that the bureau had "a lot of balls in the air" related to its ongoing work on the Khan case.