My first thoughts were, this is another example where people have access to guns in our culture, without any real control, and this is probably what happens when you have that many dangerous things available to so many young members of the society. We need to do a better job of making sure that parents and adults are more responsible at keeping dangerous objects out of the hands of children. We do it with drugs in the medicine cabinet, bleach under the sink, more effectively than we do it with firearms and explosives. I work very regularly with schools where weapons are brought by children in elementary school. It is unfortunately more common than we would like it to be.
Children regularly spend time unsupervised at home, looking for objects of interest.
It is unfortunate that they often can find guns and drugs. This crime that we witnessed was a crime in part because of the weapons that were available. Children often get into disagreements in elementary school. That's nothing new. What is new is that they often don't have the skills they need to have learned from adults to resolve these problems, and they have the means to make the consequences more dire and deadly.