Members of Congress were among the first to issue reports of shots being fired outside the Capitol, sending out Twitter messages and reassurances of their own safety. 

Sen. Claire McCaskillClaire McCaskillFive takeaways from the Georgia special election Picking 2018 candidates pits McConnell vs. GOP groups Potential McCaskill challenger has .7M: report MORE (D-Mo.) was the first member to tweet.



Initial reports suggested the shooting happened on the House side of the Capitol, but the entire complex went on lockdown, Rep. Joaquin Castro (D-Texas) said.



Rep. Grace Meng (D-N.Y.) posted a picture of a police officer pointing a gun toward the outside of the Capitol. BuzzFeed reporter Kate Nocera first posted the photo.



Other members tweeted they were told to “shelter in place,” and that their staffs were safe.



Sen. Kelly AyotteKelly AyotteHow Gorsuch's confirmation shapes the next Supreme Court battle THE MEMO: Trump set to notch needed win with Gorsuch Gorsuch sherpa: Dems giving GOP ‘no choice’ on nuclear option MORE (R-N.H.) also tweeted that she was safe and expressed concern for anyone injured. 



The House, which was in session, had to go into recess.



Multiple reports said a Capitol police officer had been shot, and was injured.



An alleged shooter was taken down, according to multiple reports.



Rep. Jared Polis (D-Colo.) tweeted the alert he received via text message.




But many lawmakers and congressional reporters said they didn’t know what was happening.