Photo Gallery: Massacre on a U.S. Army base

STORY HIGHLIGHTS

13 are confirmed dead, another 30 were wounded in Fort Hood shootings
President Obama ordered flags at federal buildings be flown at half staff until Veterans Day
Maj. Nidal Malik Hasan received deployment orders, military officials said

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A CNN Special Investigation drills down on the causes and the impact of the Fort Hood shootings, at 8 p.m. ET Saturday on CNN TV.

Maj. Nidal Malik Hasan, a psychiatrist who worked in a hospital at Fort Hood, the nation's biggest Army base, is blamed for the deaths of 12 soldiers and one civilian, military officials said.

Another 30 people were wounded; 28 of them required hospitalization. About half required surgery, and all were in stable condition Friday morning, said Col. Steven Braverman, hospital commander at Fort Hood.

President Obama, in remarks Friday morning, cautioned against "jumping to conclusions" about what had triggered "one of the worst mass shootings ever to take place on an American military base."