10 American soldiers and one civilian police officer have been killed, and 31 others have been wounded by a US Army major at the Fort Hood Military Base in Texas.

The shooting spree occurred at about 1:30 pm CT on Thursday. The shooter, who has been killed, has been identified as Major Malik Nidal Hasan, according to CNN.

The 39-year-old major is revealed to be a psychiatrist who previously worked at Walter Reed Army Medical Center but more recently was practicing at Darnall Army Medical Center at Fort Hood.

He has been scheduled to be deployed to Iraq and is known to have been upset about that, according to Senator Kay Bailey Hutchison from Texas, as cited by FOX news.

US President Barack Obama has called the incident a "horrific outburst of violence" and has promised full investigation into its causes.

Fort Hood is the single largest military base of the US Army. Since the US invasion of Iraq in 2003, the base has seen 75 suicides, more than any other US military facility.