The two soldiers followed standard rules of engagement as a suspicious truck rolled toward their convoy in Iraq.
First, they fired a warning flare. But the truck kept coming. Then, a warning shot with live ammunition. The truck kept coming.
Then, they took aim at the driver, shooting and killing him.
Yet when they searched the vehicle, they found no weapons or bombs around the dead man.
Soon, they were sitting with Minnesota National Guard chaplain Steve Timm, anguishing over whether they had committed an unforgivable sin that violated their Christian beliefs.
"It's really, really tough," Timm said, "to believe that God hates you."
Those kinds of deadly wartime encounters — and their imprints on soldiers' consciences — are the focus of a new movement among military medical researchers to study "moral injuries," the invisible scars on soldiers who believe they have committed condemnable acts.
Psychologists at the VA Medical Center in Minneapolis are at the forefront of the work, helping to define moral injury, examining how it aggravates mental disorders, and testing whether an experimental form of group therapy can heal such wounds of the spirit.