In hindsight, of course, we all wish the Virginia Tech did cancel classes and shut the university down before the second shooting. But I wonder if university officials' decision after the first shooting was really so incomprehensible.

I was at the University of Arizona in 2002, when a disgruntled student shot three professors at the College of Nursing. I work across campus, and the first information I got was that professors had been shot and the killer was still at large. As it turned out, the gunman had killed himself, but it was not until considerably later that police found his body. At the time, it seemed reasonable to keep the campus open--there was no reason to conclude one way or another to conclude that the shooter was on campus or in the city, no way to know whether people would be safer walking to cars and driving home or staying where they were. Why didn't Virginia Tech cancel classes? And...what? Tell students who lived on campus to stay in their dorms--when the shooting had been in a dorm?

My real concern here, though, is not public safety protocols after a shooting on a campus, an event that is still thankfully rare. It is all the other questions people are raising about campus security. Reporters on NBC last night were commenting with astonishment that they were able to just walk into dorms and classroom buildings. As they should be. My worst fear is that as a result of this incident, we will try to turn college and university campuses into the kinds of spaces that airports, government buildings, high schools, and wealthy neighborhoods have become--full of metal detectors, gates, and security officers. We all suffer when we lose public spaces where anyone and everyone can meet, mingle, and rub elbows. We lose a sense of the diversity of our communities, and we lose the spaces that make the open exchange of ideas possible.