There are over 100 buildings on the main campus. If each building had maybe 6 exits, that would require 600 police or security personnel. To answer your question “How difficult would it have been to mobilize and have armed personnel at each building” I would say pretty darn hard.
August 22, 2006
BLACKSBURG, Va. A manhunt for an escaped convict suspected in the slayings of a hospital guard and a sheriff's deputy shut down the Virginia Tech campus on the first day of classes yesterday as sharpshooters were posted on university rooftops and students scrambled for safety. Link
If I was a reporter, I'd be all over the difference when a couple of LE was shot vs. a couple of students.
Where did you get your facts? A map of the campus displaying the buildings which just shown on tv. It appeared there may have been 30-40 buildings. When the shooting began where were the cops? Who was storming the building? Waiting for instructions and back up?