compound where bin laden was found was surrounded, they say, by seven-foot walls. u.s. helicopter a u.s. helicopter did crash during that raid. mechanical problems are being blamed for that. that helicopter was destroyed by u.s. troops for security reasons, but again, no u.s. forces were killed in that very daring and very, very difficult operation. ali? all right. kiran, we ve been gathering our people in the united states and several locations and around the world where people have been gathering, as soon as they heard the news starting late sunday night. here at ground zero, i m just a few feet away from where the buildings were standing. around the corner is a gathering of people, though. you can see here on this video, this gathering is quite large and quite jubilant through the course of the night. what s happening right now, behind me, is we ve got street sweeping machines, busses having rolled through. the police have set up barricades, moved the folks who are here celebrat