Days after the shooting, reports in the media revealed that a Joint Terrorism Task Force had been aware of e-mail communications between Hasan and the Yemen-based cleric Anwar al-Awlaki, who had been monitored by the NSA as a security threat, and that Hasan's colleagues had been aware of his increasing radicalization for several years.
He also handed out copies of the Qur'an, along with his business cards, which listed a Maryland phone number and read "Behavioral Heatlh [sic] – Mental Health – Life Skills | Nidal Hasan, MD, MPH | SoA(SWT) | Psychiatrist".[104][105] According to investigators, the acronym "SoA" is commonly used on jihadist websites as an acronym for "Soldier of Allah" or "Servant of Allah", and SWT is commonly used by Muslims to mean "subhanahu wa ta'ala" (Glory to God)
Hasan expressed admiration for the teachings of Anwar al-Awlaki, the imam at the Dar al-Hijrah mosque in Falls Church, Virginia between 2000 and 2002. Awlaki had been the subject of several FBI investigations, and had helped hijackers al-Hazmi and Hanjour settle, and provided spiritual guidance to them when they met him at the San Diego mosque, and after they drove to the east coast.[112] Considered moderate then, Al-Awlaki appeared to become radicalized after 2006 and was under surveillance. After Hasan wrote nearly 20 emails to him between December 2008 and June 2009, Hasan was investigated by the FBI. The fact that Hasan had "certain communications" with the subject of a Joint Terrorism Task Force investigation was revealed in an FBI press release made on November 9, 2009,[113] and reporting by the media immediately revealed that the subject was Awlaki and the communications were emails.[114] In one, Hasan wrote: "I can't wait to join you" in the afterlife. Lt. Col. Tony Shaffer, a military analyst at the Center for Advanced Defense Studies, suggested that Hasan was "either offering himself up or [had] already crossed that line in his own mind." Hasan asked al-Awlaki when jihad is appropriate, and whether it is permissible if innocents are killed in a suicide attack.