WASHINGTON — The family of the alleged Fort Hood shooter held his mother's funeral at the same Virginia mosque that two Sept. 11 hijackers attended in 2001, at a time when a radical imam preached there.

Whether the Fort Hood shooter associated with the hijackers is something the FBI will probably look into, according to a law enforcement official who spoke on condition of anonymity because the investigation is ongoing.

The family of Maj. Nidal Malik Hasan, the Army psychiatrist who killed 13 and wounded 29 at the Texas military base, held his mother's funeral at the Dar al Hijrah Islamic Center in Falls Church, Va., on May 31, 2001, according to her obituary in the Roanoke Times newspaper.

In 2001, Anwar Aulaqi was an imam, or spiritual leader, at the Washington-area mosque. Aulaqi told the FBI in 2001 that, before he moved to Virginia in early 2001, he met with 9/11 hijacker Nawaf al-Hazmi several times in San Diego. Al-Hazmi was at the time living with Khalid al-Mihdhar, another hijacker. Al-Hazmi and another hijacker, Hani Hanjour, attended the Dar al Hijrah mosque in Virginia in early April 2001.

In his FBI interview, Aulaqi denied ever meeting with al-Hazmi and Hanjour while in Virginia.

Aulaqi, a native-born U.S. citizen, left the United States in 2002, eventually traveling to Yemen. He was investigated by the FBI in 1999 and 2000 after it was learned that he may have been contacted by a possible procurement agent for Osama bin Laden. During this investigation, the FBI learned that Aulaqi knew people involved in raising money for Hamas, a Palestinian group on the U.S. State Department's terrorist list.

Meanwhile, a key U.S. senator said Sunday he would begin an investigation into whether the Army missed signs that Hasan had embraced an increasingly extremist view of Islamic ideology.

Sen. Joe Lieberman's call for an investigation came a day after classmates who participated in a 2007-2008 master's program at a military college said they complained to superiors about Hasan and what they considered to be his anti-American views, which included his giving a presentation that justified suicide bombing and telling classmates that Islamic law trumped the U.S. Constitution.

"If Hasan was showing signs, saying to people that he had become an Islamist extremist, the U.S. Army has to have zero tolerance," Lieberman, an independent from Connecticut, said on "Fox News Sunday." "He should have been gone."

Hasan was breathing on his own after being taken off a ventilator on Saturday, but officials won't say whether Hasan can communicate. Sixteen victims remained hospitalized with gunshot wounds, and seven were in intensive care.

Hasan likely would face military justice rather than federal criminal charges if investigators determine the violence was the work of just one person.

There is no time limit on charging Hasan, but once he is in pre-trial confinement, the military has 120 days to start his trial, said John P. Galligan, an attorney who has represented Fort Hood soldiers but is not involved in the Hasan case. However, defense attorneys often file motions that stop the 120-day clock. Authorities have said Hasan is "in custody" in the hospital, but it's unclear if that is considered pre-trial confinement.

At the post's main church Sunday, Col. Frank Jackson, the garrison chaplain, asked mourners to pray for Hasan and his family "as they find themselves in a position that no person ever desires to be — to try and explain the unexplainable."