U.S. Army Lt. Gen. Bob Cone, right, speaks during a news conference outside Fort Hood, Texas,... 
(LM Otero/AP Photo)
The shootings at the Army's Fort Hood in Texas Thursday were an "isolated incident," according to military officials.
But there have been other attacks by military personnel in recent years – some in the United States, some in the war zone in Iraq – and they happened over a period of sustained combat and multiple deployments when increasing numbers of soldiers are experiencing Post-Traumatic Stress Disorder (PTSD) and committing suicide.
Officials are just beginning to learn the relevant details about Maj. Nidal Malik Hasan, who killed 11 people and wounded 31 before being killed himself. He was a medical doctor and a licensed psychiatrist. The shootings took place at Ft. Hood's "Soldier Readiness Center," where troops are helped to prepare for deployment. Early media reports suggest that Hasan had been heard complaining about orders to deploy and that he had been heard complaining about that.
"This is an isolated and tragic case, and we're obviously in the process of obtaining more information as the events unfold," said Defense Department spokesman Lt. Col. Eric Butterbaugh.
Attacks on fellow soldiers – particularly officers – was dubbed "fragging" in Vietnam.
Between 1969 and 1971, the Army reported 600 fragging incidents that killed 82 Americans and injured 651, according to the Associated Press. In 1971 alone, there were 1.8 fraggings for every 1,000 American soldiers serving in Vietnam, not including gun and knife assaults.
Such incidents have dropped dramatically. But in recent years there have been several incidents in the United States and Iraq. As tallied by NBC News and the Associated Press, they include:
• May 11, 2009: Five soldiers shot dead at Camp Liberty in Baghdad by Sgt. John Russell.
• Sept. 8, 2008: Spc. Jody Michael Wirawan shoots himself to death after killing 1st Lt. Robert Bartlett Fletcher at Fort Hood.
• Feb. 25, 2008: Dustin Thorson, an Air Force technical sergeant, fatally shoots his son and daughter at home on Tinker Air Base in Oklahoma in domestic dispute with ex-wife. He had been diagnosed with post-traumatic stress disorder after returning from Iraq.
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