Chants of "U-S-A, U-S-A," could be heard from the White House lawn late Sunday evening, as a mass of Washingtonians spontaneously gathered to celebrate President Obama's announcement that U.S. military forces had killed Osama bin Laden. 

At its peak, several thousand rally-ready Americans assembled along 1600 Pennsylvania Avenue, waving flags and singing the national anthem to mark the historic event. 

"I'm so overwhelmed! What a relief! I've thought of this every day, I've wondered when this was going to happen," said Allison Crowther of Nyack, N.Y., whose 24-year-old son was killed in the 9/11 attacks. "When are we gonna catch this guy? And now they find him living in a mansion? God bless these people that got him. God bless Obama for going in."