Metal detectors would have prevented this and an auto lock down if something is detected. Re-adjust to some common sense safety measures at all public facilities.
How many times have we read of a kid bringing in drugs and or weapons for show and tell this is one messed up society far too many innocent individuals get slaughtered because of some losers rant against just about everything.
How incontinent is safety for the unsuspecting. You can't walk into a court or federal building without signs that expressly detail items to leave behind.
People with mental illness need to be registered in their communities. People such as the mother need to be proactive with possible threats "they" may bring to their unsuspecting associates.