RENEE MONTAGNE, host:

There are reports that gunshots may have been fired at an office building at the U.S. Capitol. Capitol Hill Police are investigating the sounds of gunfire at the Rayburn House Office Building. That building has been sealed off.

Republican Representative Peter Hoekstra interrupted a House Intelligence Committee hearing with news of the gunfire, telling those present to remain in the room. It happened during testimony from Gabriel Schoenfeld, senior editor of Commentary magazine.

(Soundbite of House Intelligence Committee Hearing)

Representative PETER HOEKSTRA (Republican, Michigan): I'm sorry, Mr. Schoenfeld, it...

Mr. GABRIEL SCHOENFELD (Senior Editor, Commentary Magazine): That interruption is quite understandable.

Rep. HOEKSTRA: I think you saw there was a little bit of going-on here in the panel, and it was not at all any disrespect to your testimony. It's a little unsettling to get a Blackberry message put in front of you that says there's gunfire in the building.

MONTAGNE: NPR Congressional Correspondent David Welna is at the Capitol, and joins us now. Hello, David.

DAVID WELNA reporting:

Hi, Renee.

MONTAGNE: We want to stress that there's a lot that's still unclear about what exactly happened this morning. But what can you tell us, so far?

WELNA: Well, you know, I was actually at Rayburn at a press conference on my way back to the Capitol, and I came through the level of Rayburn - the garage level - where there were reports of what appeared to be gunfire.

I heard nothing. I went through security going over to the Capitol. By the time I went through the tunnel and got to the Capitol and was taking the elevator up, I ran into a policeman sprinting in the opposite direction; got in the elevator and found another policeman saying that something had happened. And then I got to the ground floor of the Capitol, and when I got out the scene was chaos. Let's take a listen to it.

(Soundbite of Capitol building's ground floor during gunfire allegations)

Unidentified Security Officer: (unintelligible) Stay to your right.

(Soundbite of panicked voices)

Unidentified Security Officer: Stay to your right!

MONTAGNE: Then, do you know what was actually happening there? Just people walking in circles?

WELNA: Well, there were hundreds of tourists all over the ground floor of the Capitol, who were being herded into lines and being told to exit from the back - the west side of the Capitol. However, when I and the tourists got there to get out of the building, we were told that the Capitol had been locked down. I ran into a Congressman who was also unable to leave the building, and there were policeman carrying automatic weapons going through the hallways - a real state of alert.

Now, there has been more information that's come out since then. The Capitol has been re-opened. The only building that is shut down now is the Rayburn Office Building, and the tunnels going into it.

But I got a report from the House Emergency Communications Center just a few minutes ago saying that the Capitol Police are continuing to investigate the reports of gunshots in the Rayburn House Office Building; that the police had completed clearing the garage levels where there were reports of these shots being heard, and that they're beginning to search the remainder of the Rayburn Building, beginning at the top floor and working down. There are four ambulances that have arrived and have parked outside the Rayburn Building, but a driver of one of the ambulances told NPR's Laura Sullivan that they were just there on stand-by; there were no reports of any victims.

MONTAGNE: So, at this point, we really do not know what happened, at all? But security measures have been tightened at the Capitol, generally. Has there been anything like this before?

WELNA: Well, there was a couple years ago. There was a gun that was detected in somebody's bag after the person had gone through, going into another office building. That resulted in an evacuation of the building. However, some of the lawmakers weren't advised then. This time, lawmakers were told to stay in their offices, to not move. And it seemed that, even though the sounds of it were chaotic, this was quite an orderly response to the incident.

MONTAGNE: Thanks very much. NPR Congressional Correspondent David Welna.

And NPR will continue to follow this story and bring you more as we learn it. Transcript provided by NPR, Copyright NPR.