(CNN) -- An Army psychiatrist accused of fatally shooting 13 at the Fort Hood, Texas, military base had asked for a Muslim cleric's advice about killing U.S. troops, according to a new interview.
Maj. Nidal Malik Hasan communicated with a radical Islamic cleric via e-mail for about a year before he went on a shooting rampage that wounded 40 on November 5, Anwar al-Awlaki told Aljazeera.net.
"The first message I received from Nidal was on December 17, 2008 ... He is the one who started messaging me," he said. "In it, he asked me whether killing U.S. soldiers and officers is legal [under Islamic law]."
Muslim advocacy groups, including the Council on American-Islamic Relations, have decried the attack and started campaigns against anti-terror and religious extremism.
"We condemn this cowardly attack in the strongest terms possible and ask that the perpetrators be punished to the full extent of the law," the Washington-based CAIR said in a statement after the attack. "No religious or political ideology could ever justify or excuse such wanton and indiscriminate violence."
Al-Awlaki said he met Hasan nine years ago while serving as an imam at a mosque in the Washington, D.C. area. He said the shooting happened about a year from the time the suspect made the inquiry.
Hasan, a U.S.-born citizen of Palestinian descent, has been charged with 13 counts of premeditated murder, making him eligible for the death penalty. Retired Army Col. John Galligan, Hasan's civilian attorney, has said his client is considering pleading not guilty by reason of insanity.
"A person can't be found guilty if at the time of the alleged defense, they lacked the mental capacity to be able to commit those offenses," Galligan said.
Al-Awlaki said he lauded the Fort Hood attack because it was aimed at troops, whom he accused of fighting an unjust war against Islam.
"It is a military target inside America and there is no dispute over that," he said. "Also, these military personnel are not ordinary; they were trained and ready to fight and kill oppressed Muslims and commit crimes in Afghanistan."
Despite his approval, Al-Awlaki said his role was only limited to Hasan's thought process, adding that he'd "be honored if I had a bigger role."
CNN's Amir Ahmed contributed to this report.