Right but it is illegal to carry a gun on a campus in Arizona, Texas (until September), and Florida so these people were breaking the law just by having a gun there. You did not mention whether the people had or didn't have a conceal carry permit, but its likely all of those people you mentioned did not have them and were carrying illegally. Given that people in Texas who have license to carry permits commit crimes at rates lower than police officers, this furthers my guess that these people didn't have conceal carry permits. 
1. "The story of Landrick Hamilton, the East Florida State College (EFSC) student who was attacked in a campus parking lot by a pair of thugs armed with a sawed-off pool cue. Hamilton was able to retrieve a pistol from his car and shot one of his attackers. While Hamilton broke no laws, the school threatened to expel him for having a gun in his car campus against school policy." (February 5th, 2014)
Sources posted in my next post because of no room left to type.