The Senate Homeland Security and Governmental Affairs Committee held the first congressional hearing Thursday on the shooting at the U.S. Army base at Ft. Hood, Texas earlier this month.  Experts discussed what might have motivated an Army psychiatrist to allegedly open fire on unarmed fellow soldiers.  Committee Chairman Joseph Lieberman said he sees the murders as part of a larger pattern of homegrown Islamic extremism, and he wants to find out whether federal agencies missed warning signs that could have prevented the tragedy. 

Senator Joseph Lieberman, an Independent Democrat, said this initial hearing set the stage for a more comprehensive inquiry by his committee into the November 5 shootings.  Lieberman said the panel will conduct the inquiry with respect for the millions of law-abiding Muslims living in the United States, and for the thousands of Muslims serving in the U.S. military.

But he warned that there is a threat from Islamic extremists living in the United States.

"We do no favor to all of our fellow Americans who are Muslim by ignoring real evidence that a small number of their community have, in fact, become violent Islamists and extremists," said Lieberman.

The witnesses at Thursday's hearing included experts on terrorism and law enforcement, but no current military leaders or FBI officials.  Lieberman said his panel does not want to interfere with the criminal investigation into allegations that U.S. Army Major Nidal Malik Hasan shot and killed 13 people and wounded more than 40 others.

One of the witnesses at the hearing was former Vice Chief of Staff of the Army, General John Keane.

"How painfully and devastatingly ironic that our soldiers were gunned down at Fort Hood, while preparing to deploy overseas to fight jihadist extremism," said General Keane. "As we are rapidly becoming aware, the preliminary reports suggest that Major Hasan himself is a jihadist extremist."

Republican Senator John McCain asked the experts whether warning signs about Major Hasan's alleged radical Islamist views might have been ignored or not passed up the chain of command because of a reluctance to appear to discriminate against Hasan because of his religion.

General Keane said that the U.S. military does not have adequate guidelines in place to define what constitutes "extremist views".

"It shouldn't have to be an act of moral courage on behalf of a soldier to have to report behavior, that we should not be tolerating inside our military organizations," he said. "It should be an obligation."

General Keane said another reason warning signs about Hasan's alleged lack of professionalism, extreme views and instability might have been ignored is because of his status as a doctor.

Republican Senator Susan Collins said the committee is seeking the answer to a number of troubling questions.

"Were numerous warning signs ignored because the Army faces a severe shortage of psychiatrists?," asked Senator Collins.

Collins said some evidence suggests that there were inexcusable gaps and communications failures among intelligence agencies and the Army about the alleged shooter.

President Barack Obama has ordered a review of all intelligence related to Hasan.  And Defense Secretary Robert Gates has ordered a broad review of the circumstances surrounding the shootings and how the military identifies service members who might be a threat to others.