Nearly eight months after hordes of pro-Trump groups — including members of a range of white supremacist and other right-wing extremist groups — attacked the Capitol during certification of the presidential election, lawmakers have finally begun investigating the origins and outcomes of that day.

The January 6 commission started its work with testimony this week from four police officers. In for Jim Braude on Greater Boston, Adam Reilly was joined by Washington Post national security reporter Karoun Demirjian and Arie Perliger, a security studies professor from UMass Lowell and the author of the book "American Zealots: Inside Right-Wing Domestic Terrorism."

Demirjian said the commissions is also a product of the political moment. “It’s also to put down a verdict that is coming at a very political time. Former President Trump still has a lot of sway still in certain factions of the GOP. It’s going to be a nail-biter of a midterm election season in Congress… so I think the fact that it’s happening now in this environment, given those political realities as well as those security realities, are kind of the dual mandates pulling at [these lawmakers].”

Perliger said the commission will help better understand the threat of extremist political groups in the U.S. “For many many years we basically ignored violence that comes from domestic political actors — we were reluctant to term these acts ‘acts of terrorism.’ For many years, terrorism was a foreign policy problem,” he said. “Finally, I think we are acknowledging that this is a substantial threat to our national security and stability of the democratic system.”

Extremist groups are not new in the U.S., but what’s different now is the ability that they have to mobilize online and spread conspiracy theories. “This is a threat we haven’t faced before,” Perliger added.

WATCH: Jan. 6 commission highlights violence and racist extremism of Capitol attack