Do we need guards for performance reviews?

The NASA shooting could have been a result of an employee getting a bad performance review. It led to a supervisor being shot dead plus the employee comitting suicide. A female hostage that was taken suffered minor injuries.

So in the case of a reactionary measure, will guards or armed officers be patrolling an agency building during performance reviews? How can we be sure if a fellow employee won't behave rationally if he or she receives a negative review? Really, if you are doing bad, then you should try to fix your mistakes. If you think your review was unjust, go up the chain and voice your feelings.

It sounds like violence is the only thing to get your words across. But in the end, how can you get a positive review if you kill your boss?