The Senate Homeland Security Committee has started the first public hearings on the Nov. 5 Ft. Hood shootings.
Committee chairman Joseph Lieberman, I-Conn., labeled the killings a "terrorist attack."
"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," Lieberman said.
New information has also been learned about the man accused of killing 13 people.
The latest information about Army Maj. Nidal Hasan include e-mails he sent to a radical Muslim cleric based in Yemen. The contents of Hasan's e-mails were not previously revealed.
The electronic messages to cleric Anwar Awlaki reveal the alleged Ft. Hood gunman looked forward to death.
"I can't wait to join you in the afterlife," Hasan wrote.
Lt. Col. Tony Shaffer is a military analyst with the Center for Advanced Defense Studies.
"It sounds like code words. That he's actually either offering himself up or that he's already crossed that line in his own mind," Shaffer said.
Hasan also asked in his e-mails whether jihad is allowed. "If there are innocents killed in a suicide attack?," he wrote.
Investigators have also learned Hasan donated $20,000 to $30,000 a year to overseas Islamic charities and was concerned over the results of an HIV test he had taken.
Congress wants to find out if federal agencies worked together properly to share information about Hasan.
"The question is were those concerns conveyed up the chain of command, and were they recorded anywhere in Hasan's personnel files and did the Army do anything in response to those concerns?" Lieberman said.
Military officials at the Pentagon have also announced an investigation into extremism in the military. The 45-day review will require all branches to see how they can prevent future incidents like the massacre at Ft. Hood.