Convert one to full auto and show me how "easy" it is- maybe you posses the machining & mechanical skills to do so- and also posses a lower receiver that has not been built to prevent its conversion.
It's "easy" in the same sense to make your own home-built suppressor, put together a fully automatic grease gun in your garage, print a plastic fully automatic lower receiver with a photo-polymer printer. How often is that done?
I've fired automatic weapons, my family even owned a few growing up, and I have bump fired ARs- IME comparing them is laughable in terms of functionality, control and use.
No doubt about it. Has it been confirmed that he used an assault rifle, most places are reporting that it was strictly handguns being used.
Assault weapon, assault rifle- potato, tomato. Interchangeable.