The only person killed on campus was the shooter. He was shot by armed campus police.
A big problem with a Gun Free Zone is after you park your car and start walking.
The law abiding citizen leaves their protection in the car and has very little or no protection against a larger, stronger and younger assailant.
Gun Free buildings or a campus can cause a Gun Free Zone to reach out for many blocks with on the street parking or parking lots that are distant from the entrances to the buildings.