It says that we as a society should not be over relying on the “responsibility” of the mass in handling deadly things such as guns. It needs strict regulations just the same way we deal with car driving. After which, though, of course there are still accidents like this that can occur. But we need to minimize the risks.
The following is the story of the mom forgeting the loaded magazine and the gun in the backpack that her son took to school and then gave to other student. No one was hurt and that was the lucky outcome. If you leave it to anybody, all of them always say they are “responsible”. But you see how people drive out there in the freeway sometimes right?