Major Nidal Malik Hasan worshipped at a mosque led by a radical imam said to be a "spiritual adviser" to three of the hijackers who attacked America on Sept 11, 2001.
Hasan, the sole suspect in the massacre of 13 fellow US soldiers in Texas, attended the controversial Dar al-Hijrah mosque in Great Falls, Virginia, in 2001 at the same time as two of the September 11 terrorists, The Sunday Telegraph has learnt. His mother's funeral was held there in May that year.
The preacher at the time was Anwar al-Awlaki, an American-born Yemeni scholar who was banned from addressing a meeting in London by video link in August because he is accused of supporting attacks on British troops and backing terrorist organisations.
Hasan's eyes "lit up" when he mentioned his deep respect for al-Awlaki's teachings, according to a fellow Muslim officer at the Fort Hood base in Texas, the scene of Thursday's horrific shooting spree.
As investigators look at Hasan's motives and mindset, his attendance at the mosque could be an important piece of the jigsaw. Al-Awlaki moved to Dar al-Hijrah as imam in January, 2001, from the west coast, and three months later the September 11 hijackers Nawaf al-Hamzi and Hani Hanjour began attending his services. A third hijacker attended his services in California.
Hasan was praying at Dar al-Hijrah at about the same time, and the FBI will now want to investigate whether he met the two terrorists.