Trying to understand the Virginia Tech murders.

This article offers a good explanation for why the Virginia Tech officials delayed for two hours before warning students after two persons had been shot.

After two people, Emily Jane Hilscher, a freshman, and Ryan Clark, the resident adviser whose room was nearby in the dormitory, were shot dead, the campus police began searching for Karl D. Thornhill, who was described in Internet memorials as Ms. Hilscher’s boyfriend.

According to a search warrant filed by the police, Ms. Hilscher’s roommate had told the police that Mr. Thornhill, a student at nearby Radford University, had guns at his town house. The roommate told the police that she had recently been at a shooting range with Mr. Thornhill, the affidavit said, leading the police to believe he may have been the gunman.

Even if they thought it was Thornhill and that he'd achieved his end, they still should have warned students that there was a gunman at large and possibly still on campus.

But this background raises another question. Why would someone commit two murders like that and then relocate to another building some distance away and perform a massacre?

It's hard to understand why someone would commit the massacre. But it's not anywhere near as hard as explaining why a person would do both things. The first murder, in the dorm, seems conventional. The second incident is horrible, but you understand it by thinking: madman.

Among the central unknowns is what prompted the gunman to move to Norris Hall, which contains engineering and other classrooms, where all but the first two killings took place. The authorities said [Seung-Hui] Cho’s preparations, including chaining the doors, suggested planning and premeditation, rather than a spontaneous event.

How do you explain a person doing both things?