Looks like armed guards are not a deterrent (links to lonestar.edu):

We employ both commissioned police officers, who have the same powers and abilities as any other police officer, as well as non-commissioned security guards. Our security guards are civilian employees that support the police department by providing extra eyes and ears, and who deal with non-police calls for service, allowing the police officers to concentrate on proactive patrol of the campuses. Police officers wear blue shirts and have badges and shoulder emblems that say “police”. Security guards wear white shirts and do not have badges. Their shoulder emblem and their photo ID cards say “Guard”. Police officers carry department-approved handguns, whereas security guards are unarmed.