In an exclusive interview with NPR, the top federal prosecutor for the District of Columbia describes how investigators are building their case.

Transcript

(SOUNDBITE OF MOB AMBIENCE)

LULU GARCIA-NAVARRO, HOST:

The sounds of the criminal activity at the Capitol. And the investigation is reaching well outside the rotunda. Because Washington, D.C. is a federal district, the person responsible for prosecuting crimes committed both on federal and local land is the U.S. attorney for the District of Columbia. NPR's law enforcement correspondent Martin Kaste spoke to the acting U.S. attorney about the massive effort before him, and Martin joins us now.

Good morning.

MARTIN KASTE, BYLINE: Good morning.

GARCIA-NAVARRO: Martin, you talked to U.S. Attorney Michael Sherwin last night. What did he tell you about, I mean, the very scale of this investigation?

KASTE: Well, he thinks there's never been a federal investigation effort quite like this with the number of potential defendants. He thinks that maybe hundreds of people could end up getting charged when this is all said and done. That would be more than during all the protests and disturbances over the whole summer in D.C. And he says also in this case, there's a much wider array of potential crimes.

MICHAEL SHERWIN: We're looking at everything from destruction of property to theft of property to unauthorized, you know, access to restricted areas to potential theft of national security information to potential murder.

GARCIA-NAVARRO: What about the other kinds of crimes that people have described, like sedition, insurrection?

KASTE: Well, Sherwin says it's not his place to get involved in the politics of words like sedition or coup. But he intends to follow the evidence, he says, to whatever charges are justified. And when you ask him whether he'd also consider charges against, say, an elected official - say, the president for inciting a riot, perhaps - again, he says he'll follow the evidence. And if it's justified, he would. One key aspect that they're still working on, though, is whether these attackers were coordinated or organized somehow.

SHERWIN: Some of these individuals we identified - look. They look paramilitary almost, right? You had the uniform. You've got communication. Those show indications of affiliation and a command and control. So I believe we are going to find those hallmarks. I can't say when. I think it could be weeks, if not months.

GARCIA-NAVARRO: Weeks or months. So if any conspiracy-style charges are still a ways off, as he's saying, what are they focusing on right now?

KASTE: Well, right now, the immediate priority is identifying and arresting people who might be immediately violent. He points to the arrest of Lonnie Coffman, a 70-year-old man from Alabama who authorities say had firearms and explosives ready in a truck near the Capitol. I asked Sherwin if the search for people like that is complicated by the fact that so few people were actually arrested at the Capitol on Wednesday, though, and that almost everybody just walked out of there. And he says he doesn't want to Monday-morning-quarterback the Capitol Police, but yeah.

SHERWIN: Hundreds fled without being stopped. So, of course, it makes our job difficult. That's why we have to reengineer what happened through cell site data, social media postings, witness statements, cameras, video camera footage. So this is a process that's going to take a while.

KASTE: Though I should add here that Sherwin also says suspects have sort of been cooperating unwittingly with all the social media stuff they've left online - the selfies, the video streams. Sherwin sort of refers to this desire people have to blast themselves online. Well, this is all evidence. And even if some people are now trying to rush to delete their accounts or their streams online, he says it's - you know, they're gathering all that up. And it's easy for investigators to send preservation orders to the tech companies to save that evidence. And Sherwin says they are doing that.

GARCIA-NAVARRO: Finally, Martin, did the U.S. attorney have any theories as to the crucial why this happened?

SHERWIN: Well, he didn't have any neat and tidy theory to offer, no. But, you know, when he talked about the tactics of what happened on the Hill on Wednesday, he thinks they may be looking more closely at what happened at certain doorways into the Capitol. There may have been some critical points of failure there.

When it comes to broader preparation for that day, he says they did have intel in law enforcement, some warnings that some people were planning something. But at the same time, I get the sense that he and others didn't see it coming, that this many people would just, as a mob, overrun the U.S. Capitol. It was sort of a carnival atmosphere beforehand when he was in the crowd, he says. And then all of a sudden, this happened. And I think they're going to be studying what happened here for a long time to come.

GARCIA-NAVARRO: That's NPR's Martin Kaste.

Thank you very much.

KASTE: You're welcome. Transcript provided by NPR, Copyright NPR.