At first purchase african M.E Church a mob forms around the children, and Scout says she can sense that they are being "advanced upon" Why?

The church members are actually both welcoming and protecting the children. At first, Scout believes that everyone is repsonding to the presence in the same way that Lula did (she was very vocal that they didn't belong there). None-the-less, the rest of the congregation moved in and chased her away with their arms open wide.

I agreed: they did not want us here. I sensed, rather than saw, that we were being advanced upon. They seemed to be drawing closer to us, but when I looked up at Calpurnia there was amusement in her eyes. When I looked down the pathway again, Lula was gone. In her place was a solid mass of colored people.