I've studied mass shootings for some time, and there are things here that don't add up. This shooter may be affiliated with a terrorist organization or genuinely* mentally ill. (or the reports are wrong) Couple of the facts that don't add up:
1) He joined the community for an extended period of time before launching his attack. Most mass shooters launch attacks shortly after reaching their target and an optimal location, presumably to maintain the element of surprise. This villain instead waited, apparently, for over an hour. That's a long time to risk detection.
2) The leader of the church and the headline victim was a state Senator. The only other mass-shooting with an elected leader that I am aware of was the Giffords shooting, and that shooter was clearly mentally ill before the shooting. His presence may not have been relevant, of course. But he "just happened" to be the leader of that church in addition to a State Senator, so it's unlikely that his death was an accident.
3) The shooter survived and escaped. Most of the time, the shooter is committing suicide by attacking people, and is doing so intentionally. The only apolitical mass-shooters I am aware of that didn't commit suicide, either themselves or via attacking police, were the Giffords and Aurora shootings, the first of which involved genuine* mental illness and the second in multiple post-event suicide attempts.
4) There are reports that the local NAACP chief was told that one of the survivors was left alive to tell what happened. If true, that is not typical mass shooter behavior. Generally, mass shooters try to maximize their kills before committing suicide, to go out with the biggest bang. They don't intentionally try to "leave one alive to tell the tale." That's something you read in sword-and-sorcery fantasy fiction.
5) That haircut is really strange, and something that's more easily done with a cheap wig than real hair. (Update: Really a stupid haircut)
So I expect one of two paths to be followed:
1) He continues attacking within a short timeframe, perhaps more aggressively now that people are on-alert.
2) He goes to ground for an extended period before launching another attack.
Either way, we may, possibly, be looking at a serial spree killer. So if you're in Charleston, keep your eyes open.
*"Genuine" here means I'm not calling him crazy just because he shot up a church. That's tautological.