On June 19, 2015, FBI Director James Comey declared that the Charleston Massacre didn't fit the definition of a terrorist act because a terrorist act is more political in nature, defined as an "act of violence done or threatened to in order to try to influence a public body or citizenry."
We, the American public, are not sure why the FBI Director feels this wasn't terrorism. The shooter was very EXPLICIT in his racist political goals, via his statements and political manifesto, of murdering as many innocent people as possible in order to influence the public.
The Charleston massacre was a terrorist act, and we need our government officials to take responsibility in handling this case as one. This includes prosecution, as well as prevention of further similar terrorist acts.