Peter Simi is a sociology professor at Chapman University and has studied extremist groups and violence for more than two decades.

Arie Perliger is a security studies professor at the University of Massachusetts Lowell. His research interests include political violence and extremism.

J.J. MacNab is a fellow with the Program on Extremism at George Washington University. MacNab is an expert on sovereign citizens, paramilitary militia groups and anti-government extremist organizations.

Gary LaFree is the founding director of the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland. He created the Global Terrorism Database.

Seth Jones is a counterterrorism expert with the Center for Strategic and International Studies. Media contact is H. Andrew Schwartz.

Michael German is a fellow with the Brennan Center for Justice’s Liberty & National Security Program and a former FBI agent who infiltrated neo-Nazi terrorist groups as an undercover agent. Media contact is Mireya Navarro.

Ruth Ben-Ghiat is a history and Italian studies professor at New York University. She studies fascism and her upcoming book is “Strongmen: From Mussolini to the Present.”

Kathleen Belew, a history professor at the University of Chicago, is the author of “Bring the War Home: The White Power Movement and Paramilitary America.”