Hmm... why does it take a ME to tell us that? Looking at shells on the ground or pictures of the perp with a rifle would have told us that. I heard reports that the ME started spewing this theory before he examined the victims...
Being the ME, he had access to all bodies prior to, and being prepped for autopsy, and full supervision of all procedures on children/adults. .223/5.56 make very distinctive entry/exit and internal wounds, compared to handguns and shotguns. He did seem to be a “quirky” kind of guy, if you watch his presser. I cringed a couple times at his answers and jokes.