I agree, which is why Police carry guns - well not all Police, ours don't carry sidearms (although they have them in a gunsafe in their cars, and the Armed.Offenders Squad are of course armed).
IMO arming teachers is not the solution, controlling the availability of hand guns, automatic weapons and ammunition might help though. We're giving it a try down here. In a year or 2 I'll come back to this thread and we'll see how many more mass shootings we've had compared to the US. If it works I'll let you know - but Australia did it 23 years ago and they haven't had any more massacres since, so I'm pretty hopeful.
I have always thought the USA was a great country and Americans good and generous people - I still think that, but it's also hard not to think that America has a real problem with gun violence.
One final note, before last week's mass shooting the most frequent cause of gun deaths in NZ were people being shot by Police - good guys with guns. Most of those shootings were of course justified.