Worshippers returned to the Emanuel African Methodist Episcopal Church in Charleston, South Carolina, on Sunday, just days after a gunman opened fire at a Bible study at the church, killing nine people. The alleged shooter, Dylann Roof, is white. The victims in the attack were black. In the days since the shootings, a racist manifesto purportedly written by Roof has surfaced, explaining why he targeted Charleston and “Mother Emanuel,” the oldest AME church in the South. President Barack Obama said the attack “raises questions about a dark part of our history,” while MSNBC’s Melissa Harris-Perry declared the shootings “an act of racial terror.” We asked Max Abrahms, a terrorism theorist and assistant professor of political science at Northeastern, about the Charleston massacre, the distinction between hate crimes and terrorism, and American views on domestic terrorism.

Were the shootings in Charleston an act of terrorism?

As I argued in my recent interview in Foreign Policy, I am very comfortable labeling the Charleston massacre as terrorism. There is no consensus over the definition of terrorism. But the standard definition among social scientists is based on three criteria. Terrorism is typically defined as an attack by a nonstate actor directed against a civilian target for some sort of political goal. In the Charleston attack, the suspect is Dylann Roof, not a government. That he appears to have acted alone in no way disqualifies him as a terrorist. Indeed, all lone wolf terrorists by definition lack operational support from a terrorist organization. The target of the attack was also clearly non-military. The nine people gunned down at church were civilian. And Dylann Roof certainly appears to have been politically motivated. He reportedly donned a pro-apartheid jacket in his Facebook profile, sported a Confederate flag license plate, told racist jokes, advocated segregation, and went on a racist rant right before the killings. This racist rant about how blacks are raping white women and taking over the world are among the most common tropes of white supremacist terrorist groups. Finally, we have learned the attack was premeditated. Roof attended the church meeting before allegedly opening fire. Authorities say he went to target practice to improve his shot. And he had told friends of his intent to kill blacks months before he carried out his plan.

On Twitter, you mentioned on Thursday that “the distinction between terrorism and hate crime can be very fine, sometimes invisible” and that the distinction “can depend more on the politics” of the labeler than the perpetrator. Has this always been true or has this distinction changed over time?

Terrorism and hate crimes share an important similarity—both inflict pain beyond the immediate victims of the attack. Terrorism is widely understood as a communication strategy in which the violence is intended to resonate more broadly by promoting fear throughout the population. Similarly, hate crimes do not just harm the proximate victims, but are designed to torment other members of the group. For this reason, both terrorism and hate crimes should and do carry stiffer legal penalties in terms of sentencing.

There is no consensus over the definition of terrorism, largely because the label is used strategically by government authorities. In Egypt, for instance, even nonviolent protesters may be deemed terrorists if their political preferences are at odds with official policy or ideology. By labeling the dissidents as terrorists, governments gain public support to crush them, often violently.

Terrorism is widely understood as among the worst offenses to society, perhaps the worst. For this reason, it is important to maintain consistency in the word’s application; otherwise, we risk diminishing certain violent incidents, like the one in Charleston.

You’ve stated that Americans haven’t historically viewed violence by white supremacists as terrorism. Why do you think that’s the case?

Conduct an experiment: Ask an American friend to name the first three terrorist groups that come to mind. Odds are the list will be of Muslim groups, such as Islamic State, al-Qaida, or Hezbollah, but won’t include the KKK. The list might include other non-Muslim groups like Aum Shinrikyo, ETA, the Irish Republican Army, or the Tamil Tigers. But the fact is that when Americans think of terrorism, they think of international terrorism—not the domestic variety.

Academics tend to exclude the Klan from the study of terrorism because of its domestic origins. Traditional terrorism datasets like the Rand-St. Andrews Chronology of International Terrorism, the State Department’s Patterns of Global Terrorism, and International Terrorism: Attributes of Terrorist Events are all restricted to international terrorist groups. Only relatively recently did other global terrorism datasets include incidents by the Klan (or any other domestic group, for that matter). For this reason, the KKK is typically missing from the secondary literature on terrorism as well. If you want to read up on the Klan, search under “hate crimes” instead.

This tendency to whitewash Klan violence from the terrorism record is ironic. Americans are often accused of being insular. But when it comes to labeling terrorists, Americans fixate on foreign perpetrators. Around the world, though, domestic terrorist attacks have actually outnumbered international terrorist attacks by a large margin.

Acknowledging that the U.S. suffers a longstanding white supremacist terrorism problem in no way diminishes the Islamic State terrorism threat at home. Both need to be combatted with vigor by the American public and government alike.