Cho's first attack after entering Norris occurred in an advanced hydrology engineering class taught by Professor G. V. Loganathan in room 206. Cho first shot and killed the professor, then continued shooting, killing nine of the 13 students in the room and injuring two others.<1> Next, Cho went across the hall to room 207, in which instructor Christopher James Bishop was teaching German. Cho killed Bishop and four students; six students were wounded.<1> Cho then moved on to Norris 211 and 204.<20> In both of these classrooms, Cho was initially prevented from entering the classroom by barricades erected by instructors and students. In room 204, Professor Liviu Librescu, a Holocaust survivor, forcibly prevented Cho from entering the room. Librescu was able to hold the door closed until most of his students escaped through the windows, but he died after being shot multiple times through the door. One student in his classroom was killed.<22> Instructor Jocelyne Couture-Nowak and student Henry Lee were killed in room 211 as they attempted to barricade the door.<23>
http://en.wikipedia.org/wiki/Virginia_Tech_massacre Barricading the door was a good idea but would have worked better if an armed student or instructor would have taken cover behind a desk with his firearm pointed at the door. When Cho would have forced his way in, the armed individual would have been able to make certain that Cho was a shooter, not law enforcement. He then could have taken careful aim and either wounded or killed Cho.
Remember that not all college students are drunken irresponsible idiots who are under the age of 21. Many are responsible adults who live off campus. Some are law enforcement personnel or ex military attending college. People who have a concealed carry permit have undergone a criminal background check and usually have training in firearm safety and the legality of using a firearm for self defense. Statistics have shown such people rarely misuse that privilege and are very responsible.
Licensed firearm owners often carry their weapons in public and there is little reason to suspect that they would suddenly become foolish and irresponsible just because they happen to be on a college campus or in a classroom.
Unfortunately in our society there exists an extremely small number of people who suffer from severe mental illness who lash out at society and run amok. Often such people look for a gun free zone. Eliminating such areas may cause them to reconsider their actions. Many areas that forbid firearms offer armed security to protect citizens. Providing armed security in all college buildings and installing scanners to prevent unauthorized people from bringing weapons is probably cost prohibitive. However, measures need to be taken to prevent massacres.
Allowing licensed individuals to carry concealed on campus should act as a deterrent. I personally would have no problem with requiring such individuals to pass further requirements before being allowed to carry in a college environment or with limiting the carry to school employees. Still some states do allow concealed carry on campus and the result have been favorable with no major problems.
Often those who oppose firearms feel that anyone who carries a weapon must be suffering from extreme paranoia or some form of mental illness. If this were true than we would see far more incidents where licensed individuals would shoot others unnecessarily. I think much of the stereotyping of gun owners and how they behave comes from the constant violence we see portrayed in the movies and on TV. You have to realize that such entertainment has little to do with reality. Reality is often boring.