Judging by how the crowd was acting that night, I don't think it's a huge stretch of the imagination to think that some of those people could have resorted to that kind of violence.

I found this video - note the people who have covered their faces. Why do that?
http://www.youtube.com/watch?v=7JamlN971AY&fe...

(The update above does mention people going outside and telling the crowd that everyone is gone. This video shows that happening.)