The U.S. Senate Sergeant at Arms Office put out word via Twitter's new alerts system that there had been gunshots Thursday on Capitol Hill.
Launched just last week, the Alerts system was designed to let public agencies and other institutions quickly alert people about disasters and other events. Today, after word began spreading about shots being fired on Capitol Hill, the Sergeant at Arms Twitter account tweeted, "USCP investigating reports of gunshots on Capitol Hill. If in a #Senate office, shelter in place. If not go to nearest office. #alert"
It's not known if any other agencies have yet to use the Alert system to spread word about an event.
In the U.S., agencies like the American Red Cross, the Centers for Disease Control and Prevention, the US Department of Homeland Security, and many others have already signed up to use the system.