Well, the goal here was to alert the parent to a concern. It was not supposed to be confrontational, after all, the child had not broken any laws. And LEO did their job, although, I think that the child should have been evaluated by a professional for danger to himself and others. And based on that assessment, a judge could have mandated counseling. They didn't go there.
Police are not professionally trained professional psychologists, and I think that the mental health aspect is often minimized by law enforcement. They really were making a "judgement" call on mental health, and should have made sure that the child was actually assessed by a psychologist. MOO.
I guess that they "assumed" that the parent was responsible and would take the alert seriously. I think that they could have also offered trigger locks at the time for his guns. Out of an abundance of caution. I know our police department has boxes of those, anyone who wants a handful can have them for free.