Nidal Malik Hasan, the man accused of killing 13 people and wounding 29 at a US army base is now capabable of speaking.

It's unclear if investigators will take advantage of his improving health to press forward with their probe into the shooting spree.

Authorities say Hasan, a 39-year-old US Army psychiatrist fired off more than 100 rounds last Thursday at a soldier processing center before civilian police shot him in the torso.

He was taken into custody and eventually moved to an Army hospital in San Antonio, where he is in stable condition and can talk.

Authorities refer to Hasan as the only suspect in the shootings, but won't say when charges would be filed and have not determined a motive.

Fifteen of the shooting victims remained hospitalized with gunshot wounds, and eight are in intensive care.

A family member says Hasan, a US citizen of Palestinian descent, has been telling his family he wanted out of the military but had been unsuccessful in his efforts to leave.

Other reports say Hasan was upset about his pending deployment to Afghanistan, which was scheduled for late November.

US President Barack Obama and First Lady Michelle Obama will attend a memorial service for the victims on Tuesday.

The attorney for Hasan says he's heading to San Antonio to meet his client.

He says he was retained by Hasan's family, and asked investigators not to question Hasan and doesn't know if he's been medically cleared to talk.