The US Capitol and its office buildings were briefly locked down Tuesday, the second time in a week amid nervousness over recent shootings. 
"The United States Capitol Police (USCP) ordered a lockdown of the Capitol Complex after reports of shots fired at Metropolitan Police Department officers, leading to a pursuit that ended at the exit of the Third Street Tunnel," the Capitol Police Board said in a statement, according to (CBS News). 
"Two suspects were arrested and taken into custody on the scene. One of the three suspects fled the scene, causing the lockdown until the suspect could be apprehended," the statement said. "Once the suspect was located and taken into custody, the lockdown was lifted".

Source : QNA