After 16 people died.
Looking forward to your handbook. Gonna be a best seller, I'm sure.
Travis
Part of what put an end to Whitman and kept more from being killed were ordinary citizens who returned fire on him and kept him pinned down.
You can't prevent nut cases from doing crazy things. You can be prepared to deal with them. That starts with the individual taking responsibility for themselves and those around them. That includes the Second Amendment and a full exercise thereof. It also includes well trained, well equipped, properly utilized law enforcement.
There is no silver bullet.