The Bump Stock Ban is based on a hoax
The firearms he supposedly used to shoot into the crowd were also supposedly fitted with bump stock devices. The ATF subsequently used that event as justification to make a rule change banning bump stocks by considering them to be machine guns -- a rule change that violates the plain language of the law.
There were a LOT of questions about that case. Lots of sketchy and contradictory stories by the police on the scene, and lots of evidence kept hidden. Now, we find out that the ATF personnel were not allowed to examine the weapons used to determine if they had been converted to machine guns. (There are ways to do that, but performing the conversion is illegal, and generally not easy, as anything that makes the process too easy is considered to be a machinegun itself).
So what if the guns the killer used were actually illegally modified machine guns, and he just happened to have some bump stock guns lying in the room but did not use them?
Well, the ban -- which will affect roughly half a million people -- would be based entirely on false premises, wouldn't it?
Why would the FBI refuse to allow the ATF to examine the guns?
To be sure, there are other possible reasons the FBI might not allow the ATF to examine the guns. A few that come to mind: did the shooter have ties to law enforcement or intelligence agencies that might have shown up if the guns were examined and (especially) their serial numbers traced?
Some people will call this a conspiracy theory. They said the same thing about the idea that the FBI were listening in on the Trump campaign, and look how that turned out. I'm not claiming to know what happened or saying it was all some sort of plot. But is it too much to ask that government agencies tell the truth, stop hiding information, and stop taking advantage of public crises like this one to advance their so-called national security policies through fear?
UPDATE: More details on the discrepancies.