I've had to point out to parents like this that currently there are three sets of parents I know of who are facing the possibility of jail time because their child brought a gun to school.

Also, teen brains are different than adults' brains. They sometimes do weird things -- even the "good" kids. They also might have mental health issues the parents don't know about/are in denial about/thought they were addressing sufficiently. Nowadays, kids might fall into weird online communities and get groomed to do any manner of things and the parents may have no idea. If someone's child -- who I'm sure is a great kid -- does the unthinkable and gets ahold of guns the parents thought were stored securely and gets the harebrained idea to bring one or more guns to school, what are these parents going to do when it's their child coming home in a bodybag? If someone at the school had to shoot their child to protect the other children, does anyone really believe that these parents will support the school's actions?