As an army psychiatrist treating soldiers returning from Iraq and Afghanistan, Major Nidal Malik Hasan had a front row seat on the brutal toll of war. It is too early to know exactly what may have triggered his murderous shooting rampage Thursday at Fort Hood - Hasan is accused of killing 12 people and wounding 32 others before he was wounded by a police officer - but it is not uncommon for therapists treating soldiers with Post Trumatic Stress Disorder (P.T.S.D.) to be swept up in a patient's displays of war-related paranoia, helplessness and fury.

In medical parlance it is known as "secondary trauma", and it can afflict the families of soldiers suffering from P.T.S.D. along with the health workers who are trying to cure them. Dr. Antonette Zeiss, Deputy Chief of Mental Health Services for Veteran Affairs, while not wishing to talk about the specific case of the Fort Hood slayings, explained to TIME that: "Anyone who works with P.T.S.D. clients and hears their stories will be profoundly affected."

It's entirely possible that other factors may have acted as a trigger for Hasan's alleged killing spree. The army major was a devout Muslim who reportedly had been harassed because of his religion and had developed strong objections to the wars in Iraq and Afghanistan. But he was also due to be shipped out to Afghanistan, drawing him closer to the terrible scenes described in detail by his patients. At army hospitals dealing with P.T.S.D. patients, the staff is required to periodically fill out a 'resiliency' questionnaire that is supposed to gauge how well they are coping with the burden of their patients' emotional and psychological demands. "It takes its toll on people," says one officer at a Colorado military hospital. "You cannot be un-affected by the terrible things these soldiers have undergone."