If she had done her job, that would have been impossible.
I looked up the regulations. She was supposed to have the gun locked up, checked it when it was taken out, handed it to him personally, waited for him to check it, and both sign off that it was cold. That did not happen. Baldwin is responsible, but so is she and so is the assistant director.
You don't know for a fact that that didn't happen. Testimony may or may not bear out that it did in fact not happen but it hasn't yet.
If celebrity crime takes the usual course we likely will never know for sure but we will be served up someone, it is the Hollywood way.