Now, what should happen now is the FBI looking into what could have been (or not) done to stop it. They're not expected to work magic, but it's still a failure. Maybe part of that anti-terrorist money bonanza would be better spent monitoring racial hate groups? Maybe not. I don't know, that why they need to look into it.
They are looking into it, always. The FBI has been repeatedly warning that domestic terrorism, and especially people talking about doing crazy shit, is the most active the FBI has seen since the mid-90s (bombs and militias and whatnot), and has been steadily building over the last five or six years. Y'know, for some reason.
The issue is, the FBI is not run by stupid people. They know exactly why white supremacist and survivalist militia groups are on the rise. They also know that anything they do to proactively ferret out potential troublemakers might just inspire more of them. Dylann Roof was the perfect example of the problem they're dealing with; until a couple weeks ago he was just another weird dude saying weird things to his close family, with no tangible connection to any of the people he claimed to be inspired by.
There's a great quote from an FBI agent that I wish I had saved, this is a big free country where people can say any hateful or stupid things they want. Saying things is not a crime, associating with people who say things is not a crime, buying the tools to do things is
usually not a crime although it definitely gets the FBI's attention. It's only the act itself that's actually a crime. And trying to keep tabs on every single unaffiliated crazy person just isn't possible, and the FBI knows that the more they try, the more they fit the stereotype these fringe groups want the government to fit, and the more they might wind up fueling the next unaffiliated crazy person.
The Oklahoma City federal building was bombed on the anniversary of the Waco ATF siege, for exactly this sort of reason. The last thing the FBI wants is to set off a chain reaction like that again.
Of course, it might help if the FBI director wasn't trying pretend
policially motivated violent isn't terrorism if it isn't foreign.