The biggest terror threat in America isn't Islamic extremists
But many people would also consider Roof's alleged actions a terrorist attack, one of 19 carried out by non-Muslim extremists on American soil in the post-9/11 era, according to data by New America, a Washington Research Center, as reported by The New York Times.
By comparison, jihadists have carried out seven such attacks over that same time span.
The study found that non-Muslim extremists are responsible for 48 American deaths - 22 more than jihadists, who have perpetrated 26, since September 11, 2001. These numbers suggest that racial hatred and government hostility inspire more terrorist attacks than religious fanaticism, typically considered a driving force of the "War on Terror."
The study, however, omits several mass shootings, including the ones in Newtown, Connecticut and Aurora, Colorado, because in both cases no ideological motive could be discerned.
"There's an acceptance now of the idea that the threat from jihadi terrorism in the United States has been overblown," John G. Horgan, who studies terrorism at the University of Massachusetts Lowell, told The Times. "And there's a belief that the threat of right-wing, anti-government violence has been underestimated."
ReutersA memorial is set at the entrance to the Sikh Temple of Wisconsin, as mourners attend a candlelight vigil on the one-year anniversary of a mass shooting in Oak Creek, Wisconsin August 5, 2013.
Jon Stewart, host of the "Daily Show" on Comedy Central, suggests Americans have formed a biased definition of terrorism.
"What blows my mind is the disparity of response between when we think people that are foreign are going to kill us and us killing ourselves," Stewart said on his show following the Charleston shooting.
"We invaded two countries and spent trillions of dollars and thousands of American lives ... all to keep Americans safe," Stewart said, referencing the War on Terror in Iraq and Afghanistan after 9/11. "But [in Charleston] we're going to keep pretending like 'I don't get what happened this one guy lost his mind'."
Others say we don't see Roof, and those who have committed similar acts, as terrorists because to some degree, they're more relatable to Americans than, say, Islamic extremists.
"Most Americans are white, and we see white people like ourselves. When I see Dylann Roof, I remember being a white male his age, barely out of my teenage years and experiencing weird anger in a difficult time," Philip Bump wrote for the Washington Post. "We can identify much more easily with who he is."
While many people have their own opinions of what constitutes terrorism, it's clear that in America today, extremist violence isn't solely an issue of religion.