Not really, not unless they hit the heart, spine or other vitals. The bullets are optimized for penetration. With bullets optimized for expansion or other exotic terminal effects (glaser safety slugs etc) we might have seen more killed and fewer wounded, with less pass-throughs and multiple hits by each slug.
I wonder what round he used (probably never find out, unless Mas Ayoob writes about it), the civilian ones are loaded with Hornady V-Max bullets, better known for their terminal performance on varmints than people. He might have gottten his hands on the LEO or Mil rounds more geared for penetration.
Either way, given the observation by the FReeper you mentioned, this wasn’t “sudden jihad” it was coldly premeditated.