People blaming the FBI, officer, school officials or the former parents are way off base......the shooter was set to kill kids at this school. Obvious the two unarmed people outside who tried to stop him didn't work..they're dead.
No stopping this killer short of another bullet.
If we don’t hold the cold who met Nick responsible for their coldness too, then we miss the point that God wanted these encounters to teach. A bad fate can be mitigated. Maybe Nick could have been humanely nudged along in life till he went to hell on his own accord.