School shooting deaths are only the beginning of tragedy. Three years after the April 20, 1999 school massacre here, the repercussions of Columbine still ripple through this Colorado community. At face value, the two gunmen — Eric Harris and Dylan Klebold, who, after killing 12 students and one teacher, turned their weapons on themselves — should bear sole blame. The reality is that grief makes people turn on each other, and in anger they lash out again and again. Still.