Pro-Trump extremists made their way into the U.S. Capitol yesterday, which sent Congress into an hours-long lockdown in the middle of formally recognizing Joe Biden as the next president of the United States. It's the first time since the War of 1812 that the Capitol has been attacked. GBH Morning Edition Host Joe Mathieu spoke with former Homeland Security official and GBH contributor Juliette Kayyem about what happened and who should be held responsible. The transcript below has been edited for clarity.

Joe Mathieu: I was talking to my 13-year-old, who was questioning a lot of things last night about our country and our government. I did try to remind [her of] the resilience of America; we are still here. Joe Biden was confirmed last night. The system worked. But why did that have to happen at all yesterday, Juliette? Why were Capitol Police not prepared?

Juliette Kayyem: So let's start with the tactical response, because this is obviously a bigger issue about what, in fact, happened and the president's responsibility for it. It's inexplicable, and there has to be an explanation provided to the American public. It's inexplicable for a number of reasons. One is at least as early as last week, the D.C. mayor seemed very clear about the concerns she had and began to pre-position assets for the area she controlled. The Capitol has its own police and law enforcement entity. So the potential threat was known to her, as well as to people like me who had been warning [that] a group is congregated. And all you have to do is go online. They were ordering t-shirts that said we're going to come.

Mathieu: They were posting images of the weapons they were bringing to Washington, Juliette.

Kayyem: Right. So this is a notice event; we should not have been caught off-guard. Then there is at least 30 to 40 minutes between when the president says essentially let's not put nice words around it let's go attack the Capitol. I mean, he uses words like "fight" and "injustice."

Mathieu: Not show weakness.

Kayyem: Yeah, not show weakness. And Giuliani did the same, the former mayor of New York. So they didn't seem to be prepared for that. And then, of course, once they enter, I will say, I do think that they were able to de-escalate a lot of it without there being a battle. I know a lot of people were like, "Where's the National Guard? Where's the military?" In some ways we do have to be grateful. A woman was killed and shot, a supporter of Trump. Three others are identified as having died in response to it. We don't know what those were. And so there has to be a reckoning in terms of both the pre-positioning and then in that half hour [to] 40 minutes what the heck were they doing? They see this crowd coming.

Watch: 'There will have to be a reckoning' within the Capitol Police Dept.

Mathieu: When you were with Homeland Security, Juliette, you guys plan for a lot of different things. Was there ever a table exercise? Was there ever a plan to deal with an attack on the U.S. Capitol like that?

Kayyem: Yes. First of all, there was a threatened attack on 9/11. It's called the National Regional Planning. So it's D.C., Virginia and Maryland, and you train and test around what assets are you moving, [and] can you get help from Virginia and the National Guard? D.C.'s lack of status means that the mayor is completely dependent on federal entities, and so she can control the streets. That's where the National Guard was put and the curfew, which is still in place, but does not have much control over the federal buildings. But certainly any of them under threat is part of our contingency and continuity of government planning.

Mathieu: It's law agency alphabet soup down there. I lived in Washington long enough to know it's Capitol Police, it's D.C. police, it's uniformed Secret Service, it's un-uniformed Secret Service. It goes on forever. Do we need a new system to coordinate this for the people who live in the district?

Kayyem: No, I think the bigger issue is, of course, statehood. I do think that this is tied to statehood. There's major areas of the District of Columbia that the mayor, who is going to have all sorts of intelligence about what's going on, cannot assert a command and control over. Anyone who's been to D.C. knows there's not like a tollbooth between where D.C. begins or where the federal assets end. I think the do-over or what needs to change is a president who promotes domestic terrorism. It is what we've been documenting for years, the way he incites his followers [and] he lies to them I'm not defending them; they should take full responsibility, but nonetheless and then creates an aura that he can plausibly deny, right? So he says, "We were robbed. We need to fight," and then shock and dismay that that's, in fact, what they do. You saw that from the Republican senators, from Hawley and Cruz. Oh, come on, guys! You know exactly how this was going to end. That's domestic terrorism and it should be called that.

"We're playing games with words in terms of 'riot', 'insurrection' or 'coup.' I don't think it's any of those. This was domestic terrorism incited by the president of the United States."
Homeland Security Expert Juliette Kayyem

Mathieu: Lastly, Juliette Kayyem, I want to ask you about what's happening at the Pentagon. We understand the Pentagon essentially cut the president out, working directly with Mike Pence to deploy National Guard troops yesterday. When you hear something like that, and by the way, the military seems to have been in a very aggressive footing lately. You're seeing the Joint Chiefs get out there. They know the vulnerabilities that this creates. Does that mean that Donald Trump is effectively no longer the commander in chief? And could he resign?

Kayyem: I wish he wasn't. He still is. But I do think what you're seeing is for the next two weeks, a military adapt around him so that they are not utilized for whatever perverse and violent activity he wants them to. So this scenario that you described in which the acting secretary of defense, Miller, made it clear: The president was not in the room when they were discussing the deployment of the National Guard.

Mathieu: That's incredible.

Kayyem: It's incredible. And there was another moment where National Security Adviser Robert O'Brien sends out a tweet only invoking the goodness and the responsibility of the vice president. The president has lost command and control over federal assets, including the military. I don't know if it's consolation, but it probably is that that is true. But I think it shows the dangerousness of the next two weeks. I have never been a proponent of the 25th Amendment, but, boy, if people have it in their minds at this stage, there's no solution for him except for taking him off the platforms, Twitter and Facebook, and trying to get a command and control system that works around him. We're at that stage where the next 13 days are unprecedented in terms of our incapacity to control a president who let's just be clear desires to burn the place down on his way out. And I'm pretty calm, but there is no other way that I can describe it to listeners.

Mathieu: Juliette, I remember in the campaign in 2016, so many of his supporters said it's not about even politics or policy, we just want him to go down there and break it. And he certainly tried to. I don't know if he did.

Kayyem: No, I think the Republic still stands. We've got 13 more days to go. I think there's one image, if I could just end with this, that describes his treachery and I think the treachery of the Republican Party that footsied with all of this and then was shocked. Senator Josh Hawley, the pretty boy or so he thinks, who's so concerned with election fraud and was leading the effort to not have Biden be president, although he would never put it that way, there's a picture of him now of his fist held high, rallying the mob. This is before they came into the Senate. And you think this is treachery in suit and tie, right? This is what has happened. And then shock and dismay that, in fact, the mob had listened. So there is a lot of blame to go around, but it begins, of course, in the Oval Office. So 13 more days, if not less.