From what I have read, many of the dead and wounded were hit multiple times so it was quantity over quality. I bet he shot most at point blank range while they were cowering on the ground.
Must have been so. He had them cornered and surprised. Still... remarkable quantity. If only some students or professors or security people were armed. These days, especially in New York, if we go armed, we’re considered potential terrorists. So, we’re either victims or villians.
I think most of his victims were in a single classroom, also. It was like shooting fish in a barrel; I don’t think any great skill was involved.