I haven't seen this clip before. It's right at the end and it sounds like the reporter is talking about Building 6 exploding. I can't read it any other way at least. He says "another building has gone up" so he can't be talking about the south tower.
There seems to be an audible explosion aswell but it hard to say. It could be a number of things I suppose.
Do we have any idea who the reporter was or what station he was from?