Fort Hood shooting suspect faces 13 murder charges

The counts are initial charges against Maj. Nidal Malik Hasan, and more are possible, Christopher Grey, a spokesman for the Army's Criminal Investigation Division, said at a news conference Thursday afternoon.

The charges make Hasan, 39, eligible for the death penalty if he is convicted.

Hasan is accused of firing more than 100 rounds in a soldier processing center at the Texas military base on Nov. 5. Authorities have not offered a motive for the shooting.

"Our investigation remains open and ongoing," Grey said. "Let me reassure the American public that we are doing everything possible and we are looking at every reason for this shooting. We are aggressively following every possible lead."

Grey declined to release any new details of the shooting but said investigators still believe Hasan acted alone in the rampage.

Since last week's shooting, a picture has emerged of Hasan as a man who was forcefully opposed to the wars in Iraq and Afghanistan, was trying to elude his pending deployment to Afghanistan and had struggled professionally in his work as an Army psychiatrist.

Grey said Hasan has legal representation and is still being treated in a local hospital. He would not provide any information about his medical status.