A sergeant comforts a fellow soldier outside the army base in Texas. (AP)

Texas, Nov. 6: An army psychiatrist facing deployment to one of America’s war zones has killed 13 people in the largest active duty military post in the US in the worst mass shootings ever at a base in the country.

Major Nidal Malik Hasan, the suspected gunman of West Asian descent, has been shot four times and is on ventilator in a hospital after the rampage at the Fort Hood army post in central Texas. Of those killed, one was a civilian and 12 were soldiers.

Less than 24 hours later, another shooting struck an office building in Florida. At least eight people were injured but local media said two were killed. ( )

Hasan, 39, was about to be deployed to Iraq or Afghanistan, and shouted “Allahu Akbar” before opening fire, a witness said.

Clad in a military uniform and firing an automatic pistol and another weapon, Hasan, a balding, chubby-faced man with heavy eyebrows, sprayed bullets inside a crowded medical processing centre for soldiers returning from or about to be sent overseas.

The victims were cut down in clusters, officials said. Witnesses told military investigators that when the gunfire stopped, soldiers schooled in battlefield medicine ripped their clothes to make tourniquets and bandages.

Sirens typically used to warn of tornadoes sweeping across the plains alerted residents, schools locked down and the Fort Hood community struggled to understand what had just happened.

Fort Hood, named after a general and 160km south of Dallas-Fort Worth, is a virtual city for more than 50,000 military personnel and 150,000 family members and civilian support personnel. It has been a major centre for troops being deployed to or returning from service in Iraq and Afghanistan and is considered one of the safest places in the world.

A woman police officer is being credited with stopping the shooting rampage. Responding within three minutes of an alert, Fort Hood police sergeant Kimberly Munley shot the gunman four times despite being shot herself. Munley’s condition is said to be stable.

Born and reared in Virginia, the son of immigrant parents from either Jordan or Palestine, Hasan joined the US Army right out of high school, against his parents’ wishes.

Military records indicated that Hasan was single, had never served abroad and listed “no religious preference” on his personnel records.

Fox News quoted a retired army colonel, Terry Lee, as saying that Hasan, with whom he worked, had voiced hope that President Barack Obama would pull American troops out of Iraq and Afghanistan, had argued with military colleagues who supported the wars and had tried to prevent his own deployment.

Obama called the shootings “a horrific outburst of violence” and urged Americans to pray for those who were killed or wounded.

The Muslim Public Affairs Council, speaking for many American Muslims, condemned the shootings as a “heinous incident” and said: “We share the sentiment of our President.”