Update: According to CNBC the lockdown has been lifted. This video clip also includes an eyewitness description of what happened:

BREAKING: White House lockdown lifted after shooting nearby; eyewitness describes the scene. https://t.co/VGSqEAh7oGhttps://t.co/D447b04KI1

— CNBC Now (@CNBCnow) May 20, 2016

[End of update.]

Reports are just starting to come in on Twitter:

Shooting near the White House involving a uniformed Secret Service agent has the mansion on lockdown per @BennettJohnT @CQnow

— Adriel Bettelheim (@abettel) May 20, 2016

Security alert at WH. Armed Secret Service on WH roof. pic.twitter.com/Rt5LiAeHC3

— Mark Knoller (@markknoller) May 20, 2016

#BREAKING Some sort of incident happening near the White House. WH security increased. This pic taken moments ago pic.twitter.com/Krct0KoPFX

— John Zuchelli (@tvzuke) May 20, 2016

Shooting on W. Executive Dr. PIO en route to 17th and Pennsylvania

— USPPNEWS (@usparkpolicepio) May 20, 2016

#BREAKING Shooting reported near the White House. Colleague Leland Vittert rpts USSS ran thu Lafayette Park w/guns drawn. Helos overhead

— Chad Pergram (@ChadPergram) May 20, 2016

The President is not at the White House (he was apparently off playing golf). However it seems VP Biden was there:

VP Biden is “within the complex” at the White House but is “secure” – after shooting incident near White House – @jparkABC

— Heidi Jensen (@HeidiJensenABC) May 20, 2016

The White House press corps was also there when the shooting took place. Cheryl Bolen is a White House reporter for Bloomberg:

I'm at the WH and Secret Service is running around outside looking very serious-we're in lockdown now

— Cheryl Bolen Smelson (@cherylbolen) May 20, 2016

All I saw before being told to go back into briefing room were agents on the roof with really big guns.

— Cheryl Bolen Smelson (@cherylbolen) May 20, 2016

We've just been asked to go downstairs to #WHbasement to 'shelter in place.'

— Cheryl Bolen Smelson (@cherylbolen) May 20, 2016

One person has been shot and transported to the hospital:

UPDATE: Shooting at 17th and E Sts NW – 1pt transported with critical injuries to a local hospital #dctraffic

— DC Fire and EMS (@dcfireems) May 20, 2016

Secret Service agents shot an armed man at a White House checkpoint. Building is on lockdown. Obama is not there. https://t.co/VCnaNRNSXR

— Liam Stack (@liamstack) May 20, 2016

This brief clip from CBS News gives an idea of where the shooting took place relative to the White House:

MORE: Details revealed on reported shooting near @WhiteHouse; police patrolling grounds https://t.co/aDIOTPJg6X https://t.co/BeORXUkZ3y

— CBSN (@CBSNLive) May 20, 2016

#WhiteHouse shooting Suspect "brandished" weapon on 17th & E NW checkpoint. Security engaged him, shot in abdomen, in custody. (CNN)

— Joyce Karam (@Joyce_Karam) May 20, 2016

A look at the partial lockdown outside the White House after reports of a shooting near the building pic.twitter.com/fyX2wDVcjP

— Mark Meredith (@markpmeredith) May 20, 2016