I asked my husband this same question and he said it was "possible", with special modifications. Seems a bit odd that someone who has obviously meticulously planned this and so far managed to elude capture would just leave this weapon, wrapped in a towel with shells in the chamber?

I suspect the brain drain significantly impacted the ability to respond. Plus all the chaotic information being released by FBI, "we have the shooter", oh wait we don't," now we do", oops sorry wrong again, feels more like keystone cops than the FBI....