(ABC News) -- A burst of pops from firecrackers lit directly in front of 1600 Pennsylvania Ave. sent the White House into lockdown shortly after 6:30 p.m. tonight.
As crowds of tourists milling about in the street looked on, Secret Service agents tackled a man on the sidewalk just steps from the Northwest Gate.
The suspect appeared to be a middle-age Caucasian man, wearing shorts and a blue T-shirt. Three uniformed Secret Service officers put him in handcuffs on the ground.
Immediately after the disturbance, Secret Service hurried all reporters, camera crews and network news correspondents inside the building, while armed agents inside the White House grounds took up positions behind trees on the North Lawn.
The lockdown lasted for nearly a half hour until Secret Service deemed the threat cleared.
The incident came in the aftermath of the Navy Yard shooting in which a former Naval reservist Aaron Alexis killed 12 people before being killed in shotout with cops. Before the White House scare the Senate was locked down as a precaution and the Washington Nationals baseball game was postponed.