I sometimes have students indignantly query as to why they are not allowed to carry firearms on campus. Some call the rule "ridiculous." After all, they are responsible, law abiding gun owners. Well, the shooter in the incident described in this video was also, ostensibly, a responsible, law abiding gun owner - until he wasn't any longer. Everyone starts out as "law abiding" until they no longer abide by the law. When that time comes, the consequences to others are much different depending on whether the former "law abider" is armed or not.