No idea what’s happened, but the Capitol is being locked down. Per NRO’s Robert Costa, members of Congress were outside at the time but no word yet on whether anyone’s hurt. Stand by for updates.

Horrible news coming over the police radio in House press gallery

— Robert Costa (@costareports) October 3, 2013

Cops sound frantic, lots of scratchy noise and screams

— Robert Costa (@costareports) October 3, 2013

Update: They may already have the shooter:

I am told shooter has been arrested. House floor activity stopped for now.

— Tim Griffin (@timgriffinark) October 3, 2013

No word on injuries yet, if any. For what it’s worth, GOP Rep. Sean Duffy had a weird altercation outside the Capitol last night with a strange man, who screamed at him and grabbed his arm. I’m mentioning that not because there’s any evidence linking that with the shooting, but because it’s an odd coincidence that there’d be violence of any sort outside the Capitol twice in a span of 12 hours.

Update: MSNBC says a U.S. Capitol police officer has been shot. I’m seeing rumors on Twitter that it’s related to a car chase but no confirmation.

Update: More on the car chase:

Cops were chasing a black car near the Capitol building. They cornered the car and that's when shots rang out.

— Chris Moody (@moody) October 3, 2013

NBC employee on @msnbc: 10 or 15 gunshots in rapid succession. Police were chasing a black vehicle up Constitution Ave

— Domenico Montanaro (@DomenicoNPR) October 3, 2013

Update: “Capitol police tell National Journal that there are injured USCP officers, but the numbers are unconfirmed.”

Update: Hmmmmm.

https://twitter.com/paulafaris/status/385837311017357312

Update: Reports now of one dead — the person behind the wheel of the car:

BREAKING: @ABC's @MLevineReports: Source says female suspect reported dead on scene on Capitol Hill

— Karen Travers (@karentravers) October 3, 2013

Update: At just before 3 p.m. ET, the lockdown in the Capitol has been lifted.

Update: The driver had a baby in the car with her. The baby’s reportedly unharmed.

Update: Surprise — early reports may have been wrong.

Hey journos: Nobody rammed the WH "gates" — the car hit a stanchion a block beyond the security perimeter

— Glenn Thrush (@GlennThrush) October 3, 2013

Update: Some good news: The Capitol police officer who was injured wasn’t shot.

Update: Jake Tapper’s show is reporting that all of the shots came from police.

All the shots came from law enforcement, reports @DebFeyerickCNN. #TheLead

— The Lead CNN (@TheLeadCNN) October 3, 2013

Update: Madness via Ace.