My heart goes out to the families of the victims...

I don't want to detract from the main point of this thread by making it into another political discussion but...
Gun law is based upon the mistaken premise that a <person> who is willing to commit murder, rape, kidnap, terrorism or robbery will obey a law which forbids him from illegally equipping himself with a tool to make those things easier.
Gun law removes weapons from the law-abiding, not from criminals - all I can think is that if the teachers had been armed, the killer might have been stopped at two or three victims instead of 20.
And I thought the same after Dunblane, and Hungerford, and the Lakes shootings, and the St. Lukes Machette attack, and Columbine and...
Having said that - murder rates for the UK, with some of the strictest gun laws in the world, has a murder rate of 0.8 people per 100,000 (2011) compared with an average of 4.7 in the USA.
However Texas, where everyone is habitually armed has a murder-rate of 4.4 (less than average), compared to Washington DC (stricter gun laws) with a rate of 21.9 (2010 figures)