Even more of a mystery than what happened preceding the incident may be why it happened at all. Newhouse said that even though the alleged killing spree comes on the heels of the killings of two U.S. soldiers after a wave of anger sparked by the burning of several Korans by the U.S. military, these events are "unlikely to have been causative" of the massacre.
Lieberman speculated that one of three types of psychological situations could have led to the rampage: a psychotic break, an accumulation of resentment and anger, or simple sadism.
In a psychotic break, Lieberman said, the soldier would have experienced the onset of a psychotic disorder, such as schizophrenia, affective psychosis or stress induced psychosis. "This could have led him to carry out actions that seem irrational and don't make sense," he said. "Such an incident recently occurred with Jason Loughner in Arizona."
Lieberman said a buildup of resentment could have also led to the soldier's alleged unprovoked actions. "He could have endured the loss of friends and colleagues in the context of his service in Afghanistan," he said. "This anger and resentment could have led him to redress these losses and abuses in an impulsive act of violence. This seemed to have been the scenario of Lt. William Calley at My Lai Massacre in Viet Nam."
The third scenario, Lieberman said, is that the soldier is "a sociopath who [is] severely sadistic. If so he might have lacked any moral structure and acted to satisfy his feelings without ethical or moral constraint and feeling for human decency. This seems to have been the case with Charles Graner at Abu Ghraib."
Whether any one of these scenarios -- or something different altogether -- most accurately represents what happened near Kandahar on Sunday remains to be determined. Until then, Newhouse said, it will be impossible to reach a solid conclusion.
"The last comment I would make is a similar comment to the one that I made to the press after the Major Hassan incident at Fort Hood, namely that it is unwise to make general conclusions from extraordinary events," Newhouse said. "Thus I would suggest that people do not rush to judgment regarding the causes of this incident until further is known about the individuals mental state."