It didn't just happen at the camps.
Such incidents are common in war. People don't like being shot at or seeing their buddies blown to pieces. Our troops killed prisoners on D day, and all the way up to the end of hostilities. It's a common reaction when your enemy is delivered into your hands. Even after the war, there were reports of German prisoners dying from thirst will only several hundred yards away from a river. It's a terrible truth, but all sides are guilty of such actions during war.