Oh, Geez. Now some chippy on CBS wants to know how easy it is to obtain the firearms used in this shooting in Las Vegas. Here comes the ban guns movement again.
From what's been reported, the man had multiple firearms in the room. Yes, you can legally purchase Class III weapons, but the process is long and the weapons are expensive. Modified weapons often fail, due to the inferior parts, lack of expertise on the installer, or tolerances of the original equipment. Given the amount of weapons at the scene, I wouldn't be surprised if some had been altered with a 'bump fire' device. They're easily obtained, legal, and relatively inexpensive, compared to a standard full auto.