By now, members of the national press have descended on Fort Hood, Texas to tell the story of the worst soldier-on-soldier massacre in U.S. military history.

Their job will be fraught with professional and emotional pitfalls. One of the biggest, and the one that poses the greatest potential danger at this point, concerns the “why” of the rampage that left thirteen people dead and thirty injured.

It’s important to remember what we don’t know: Why Maj. Nidal Malik Hasan, a psychiatrist, opened fire in a crowded medical processing center at the country’s largest active duty military post.

What we do know: He is an American-born son of immigrant parents; a devout Muslim, according to a former imam; opposed to the wars in Iraq and Afghanistan, according to at least one former colleague; and increasingly disillusioned with the military and fearful of being deployed to a war zone, according to a cousin.

One of the challenges journalists face in reporting this story is to avoid fanning suspicions that Hasan’s was an act of Islamic extremism without hard evidence to support that claim.

Speculation of this sort can quickly go viral and become very dangerous, as was evident following the April 1995 bombing of the Murrah federal office building in Oklahoma City, which left 168 dead and nearly 700 injured. Happening just two years after the first bombing of the World Trade Center by Islamic terrorists, few imagined that such a massacre could have been committed by Americans.

Some national television reporters and columnists in major newspapers fueled the assumption that the car bombing had strong parallels to and probable roots in Middle Eastern terrorism.

In the three days before the arrest of Timothy McVeigh, later convicted and executed for his role in the bombing, the Oklahoma City area experienced a wave of physical and verbal harassment of mosques and people who were or appeared to be Muslim.

In many ways Oklahoma City, where many people worked in or knew workers in the Murrah building, is very much like Killeen, Texas, an Army town where many may have some connection to those killed or injured at Fort Hood.

While some reporters will pursue information on the post to the extent the military permits, many will swarm into Killeen’s diners, barber shops, hair salons, and other gathering places, seeking anything to enhance and advance the story.

From my experience covering massacres—including those at Oklahoma City, Columbine High School, and Virginia Tech—their window of opportunity for this will be limited.

In the first few days after such an incident, many people are happy to talk, clearly finding it somewhat cathartic to discuss their connection and response to the disaster with a sympathetic listener.

But, within a few days, the arc of the story often takes a different turn. Particularly in the cases of Columbine and Virginia Tech, students began to resent and rebuff inquisitive reporters. Within four days, the Virginia Tech administration, initially so accommodating, made it clear that journalists were no longer welcome on campus.

Reporters must be sensitive to that and step lightly. Of course, by then, the story often has moved well off the front page, and news organizations move on.

But the effects of such bloody stories on the journalists who cover them may not fade away so swiftly. Most reporters aim to keep an emotional distance from the tremendous pain and loss they are witnessing while remaining empathetic to those they are interviewing. Often, just keeping their focus on gathering accurate information and writing it in the most evocative way possible can help reporters maintain a sense of calm.

But, often for no clear reason, some disasters strike some journalists deeper than others. Maybe it was the gaping hole in the Murrah federal building with the mangled guts of its offices so brutally exposed. Or maybe it was the pastel-clad bodies of babies carried from the rubble of the daycare center. But, for me and some of my colleagues, Oklahoma City was one that made us cry.

Lisa Anderson is a 2009-2010 Encore Fellow at CJR. She was the the New York bureau chief and a national correspondent for the Chicago Tribune until December 2008.