President Barack Obama on Saturday promised a "careful and thorough" probe into the Fort Hood military base shooting, focusing on how the rampage that killed 13 people might have been prevented.

In his weekly radio and internet address, Obama said the probe "will look at the motives of the alleged gunman, including his views and contacts."

He added that "given the potential warning signs that may have been known prior these shootings, we must uncover what steps if any could have been taken to avert this tragedy."

Obama on Thursday ordered the investigation into last week's shootings, allegedly by army psychiatrist Major Nidal Malik Hasan. In addition to the dead, some 42 people were injured.

Hasan has been charged with 13 counts of pre-meditated murder after opening fire on his fellow soldiers at the military base's troop readiness center.

"The purpose of this review is clear: We must compile every piece of information that was known about the gunman, and we must learn what was done with that information," Obama said in remarks that aired on radio and via the internet Saturday.

"Once we have those facts, we must act upon them. If there was a failure to take appropriate action before the shootings, there must be accountability." the US leader said.

"Beyond that -- and most importantly -- we must quickly and thoroughly evaluate and address any flaws in the system, so that we can prevent a similar breach from happening again," he said.

Obama added that he found it "unthinkable that so many would die in a hail of gunfire on a US Army base in the heart of Texas -- and that a fellow service-member could have pulled trigger."

This video was published by the White House on Nov. 14, 2009.

With AFP.