HARI SREENIVASAN, PBS NEWSHOUR WEEKEND ANCHOR:

Despite the nation's intense national focus on Islamic terrorism since 9/11, homegrown, right wing extremists have also killed dozens of Americans. The groups include white supremacist and neo-Nazi groups and anti-federalists militias. Since 2001, the number of violent attacks on U.S. soil inspired by far-right ideology has spiked to an average of more than 300 a year, according to a study by the Combating Terrorism Center at West Point.

A 2015 survey of U.S. law enforcement groups found they consider anti-government violent extremists to be a more severe threat than radicalized Muslims. And while jihadist terrorists have killed 95 people in the U.S. since 9/11, far-right extremists have killed 68 during the same time, including the car attack in Charlottesville. That's according to data collected by our next guest, Peter Bergen, the director of the national security studies program for New America and a terrorism analyst for CNN.

Peter, I know you focus a lot of jihadists, you know, Islamic terror happening in the United States and happening overseas. But you have also been studying and looking closely at kind of home grown terror, domestic terror threats. When you saw what happened yesterday, what went through your mind?