Born in New Mexico , al-Awlaki has used his website to encourage Muslims around the world to kill U.S. troops in Iraq and has been tied by U.S. intelligence to the 9 / 11 hijackers , underwear bomber Umar Farouk Abdulmutallab , as well as Maj. Nidal Malik Hasan , the Army psychiatrist accused of killing 13 people in November at Fort Hood , Texas .