Clearly the system can't protect you as its happening much less act on serious red flags well before it. We have seen this before many times unfortunately. FBI included. I have no other reason other than to believe that they allow it. Because if they truly are that incompetent, we are fucked.
Not just allow but groom and supply weapons.
If this guy was military trained and still part of why wasn't he wearing his issued body armor, no spare mags? Something doesn't add up to me.