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The emotional impact of school shootings has sparked a booming school safety industry. In 2017, the market for security equipment in the education sector was estimated at $2.68bn, according to industry analysts at IHS Markit. Some companies have capitalized on parents’ fears by selling bulletproof backpacks or whiteboards, as well as offering ways to fortify school buildings against attack.

While refusing to pass substantive gun control restrictions, Congress has approved hundreds of millions of dollars in federal spending to help put police officers in public schools, including $45m in 2013, the year after the Sandy Hook elementary school shooting.

Some gun rights advocates have pushed to expand gun-carrying in schools further. Andrew McDaniel, a state legislator in Missouri who introduced legislation last year to make it easier to carry guns in schools, told the Guardianthat, in rural schools where it might take 20 or 30 minutes for law enforcement to respond to a school shooting in progress, it made sense to have other armed citizens ready to step in.