Samuel Sinyangwe, a civil rights activist who has helped chronicle violence against African-Americans, wrote on Twitter: “#CharlestonShooting terrorist wore an Apartheid flag on his jacket. If a Muslim man wore an ISIS flag, he wouldn’t get past mall security.”

The definition of terrorism is a shifting and contentious subject, usually with political overtones. The antagonists in the Syrian war and the Israeli-Palestinian conflict, for example, routinely accuse each other of terrorism. Militant organizations such as Al Qaeda and the Islamic State, which consider themselves liberators, are officially regarded by the United Nations, among others, as terrorist groups.

Webster’s New World College Dictionary defines terrorism as “the use of force or threats to demoralize, intimidate and subjugate, especially such use as a political weapon or policy.”

Civil rights advocates said the Charleston attack not only fit the dictionary definition of terrorism but reflected a history of attempts by the Ku Klux Klan and other white supremacist groups to terrorize African-Americans.