>So it's the state shooting children in schools
Likely, yes. Pretty much all terrorism is planned and executed by state sponsored actors.
Discussion
Are you living under the rock or something? The majority of events, tagged as terrorism, are always supported by some state. Not excluding the United States.
https://en.wikipedia.org/wiki/United_States_and_state-sponsored_terrorism
The United States has at various times in recent history provided support to terrorist and paramilitary organizations around the world. It has also provided assistance to numerous authoritarian regimes that have used state terrorism as a tool of repression...
There's a world of difference between your society - the state that you democratically form, and whose values you defend, and someone elses state.
How is enabling gunmen from our society to shoot our children, protecting us all from the actions of an external state?
It seems to me that is a conflation of different, and unrelated, issues in order to justifying an action that lacks a logical defence.
Criminality is criminality. A strong united society can stand better against it, than one riven by division and fear, and fighting amongst itself.
You asked for evidence, I gave you the evidence. Evidence of your own government killing their own people. The same people you want to take the guns from.
Stop moving the goalposts and look at the issue from a different perspective.