The FBI has released another set of documents on Samir Khan, the Charlotte, North Carolina man who blogged about jihad, went on to edit Al-Qaeda's official magazine Inspire, and was killed in a 2011 CIA drone strike in Yemen along with the radical preacher Anwar Al-Awlaki.

In September, VICE News reported on the first set of documents on Khan the FBI turned over in response to a Freedom of Information Act request. Those documents indicated that the FBI began its probe of Khan in 2006 based entirely on what the bureau referred to as "jihadist" blog posts to Inshallahshaheed, an Arabic phrase that means "Martyr, God willing." It is extremely rare for files on accused terrorists to be released by the government; historically, they have remained classified.

The latest batch of heavily redacted investigative files reveal that the bureau had grown increasingly concerned over Khan's anti-American screeds posted to his blog and determined he was a serious threat.

"Charlotte Division [redacted] to determine Samir Khan's threat potential based on his online and anti-US and jihad rhetoric," says a December 11, 2007 FBI file. "Samir Khan continues to post blogs on the internet which advocate and encourage violence. Given the totality of these indicators, Charlotte consider Samir Zafar Khan a threat."

The bureau also singled out an interview Khan gave to the New York Times in October 2007 as evidence of his Islamic radicalism. In November 2007, according to one file, a special agent at the FBI's Charlotte field office requested permission to monitor Khan via closed-circuit television (CCTV).

"Authority is requested to utilize CCTV coverage of an exterior public area or an interior common area where no reasonable expectation of privacy exists," the agent wrote. "No SOUND authority is being requested. There will be remote monitoring in that the camera will not be physically held by an Agent or consenting party. No consenting party is required to be in the area to be viewed for this CCTV-NO SOUND authority."

The agent added that because Khan was the subject of a criminal investigation "the provisions of the Attorney General's Guidelines for Foreign Intelligence and Foreign Counterintelligence investigations do not apply." In other words, the agent argued, because there would not be a reasonable expectation of privacy in the area of surveillance, the bureau did not need to secure a warrant from a special surveillance court.

Although the 250 pages of documents reveal that Khan was under heavy surveillance and the FBI had cultivated confidential sources who provided information to FBI agents about Khan, he somehow managed to flee the US in 2009 and travel to Yemen undetected.

The FBI withheld more than 700 pages of documents on Khan on national security grounds and other exemptions. The files were maintained in an investigative file in the FBI's Charlotte field office.