No eye, the kids are dead because some jackwagon decided he wanted to kill them...
That was a necessary element for the crime to be committed. However, a defended school would have either stopped the crime in the first place, because the criminal would, knowing that someone would be shooting back, have chosen a softer target, or stopped the crime in progress, before anywhere near as many children died, because someone defended them.
We cannot control the crazies and the thugs, much as the anti-gunners think we can. We can only determine our response. It is our response, not the actions of nuts and criminals, that will impact the outcome. The action we collectively chose (or collectively allowed) was to protect the children by not giving anyone permission to have the means necessary to defend the children--and that is why they are dead.
When making decisions to influence future events, it is a waste of time to focus on that which we cannot control. We should focus on how we choose to react to uncontrollable events to increase the probability of the most favorable possible outcome. Even focussing on, "He's the bad guy. Hold him solely responsible," will not stop the attacks. I am not saying we shouldn't (even if the shooter's intent is not to die on the scene anyway) hold them responsible for their actions. We should, and I applaud Colorado for not saving the time, effort, and money, for continuing the push to put a needle in the Aurora shooter's arm. I am just saying that the one useful thing that we could have done to save all (or, at least, the vast majority) of those children's lives, allowing the adults to defend those children with guns, was
prohibited in the vain and moronic idea that such a prohibition would protect the children from a crazy shooter.
The blood of those children is on the hands of those who could have rationally acted in a way to help those children survive. Yes, it is also on the hands of the irrational nutjob who shot them, but doing anything about him is beyond our control. Even potential needles in the arms won't stop these guys. Guns at the scene will.
So, primarily hold responsible those who could have prevented this crime and deliberately chose not to do so: The People who allowed their representatives to collect their most precious children in one defenseless place where a lunatic, whom we had no hope of control, could kill them unfettered by even the desire to defend them, let alone the means.