The Army will conduct an internal investigation to examine whether it missed warning signs about Maj. Nidal Malik Hasan, the man accused of killing 13 people in the Nov. 5 shooting spree at Fort Hood, Texas, two newspapers reported Monday.

Citing anonymous officials, The Wall Street Journal said the probe would focus on Hasan's six years at Washington's Walter Reed Medical Center, where he worked as a psychiatrist before he was transferred to the Fort Hood army post in July.

The Washington Post reported that Gen. George W. Casey Jr., the Army's chief of staff, is forming the investigative panel. It "will look longitudinally across Hasan's entire career to figure out how did this happen and what can we do to stop it from happening again," an anonymous Army official told the Post.

The doctors who oversaw Hasan's medical training had discussed at a meeting concerns about Hasan's overly zealous religious views and strange behavior months before the attack, a military official told The Associated Press last week. Hasan also was characterized as a mediocre student and lazy worker, but the doctors saw no evidence that he was violent or a threat. The military official spoke on condition of anonymity because the official was not authorized to speak publicly about the meeting.

The FBI learned late last year of Hasan's repeated contact with a radical Muslim cleric in Yemen who encouraged Muslims to kill U.S. troops in Iraq. President Barack Obama already has ordered a review of all intelligence related to Hasan and whether the information was properly shared and acted upon within government agencies.

The Senate Homeland Security and Governmental Affairs Committee on Thursday will hold its first public hearing about the incident. Obama on Saturday urged Congress to hold off on any investigation, pleading for lawmakers to "resist the temptation to turn this tragic event into the political theater."

Lt. Col. Richard Spiegel, an Army spokesman, would not confirm the Army probe but told the Journal: "We're going to take a hard look at ourselves and the non-criminal aspects of this case. We are still developing what that hard look is going to look like."