It's not clear from the reports whether anyone actually saw it in real life, or if it was visible only on the security cam (that's the way I'd bet), and it's the lack of salient details like that that lend credibility to all sorts of extraordinary claims. Whatever it is, it's always in the foreground, as karrie observed, and it's very blurred, which suggests it's something on the camera lens, like an insect or a speck of ash being moved about by air currents. It might also be just some glitch in the electronics. Digital sensors can produce all kinds of strange artifacts, especially the low-res ones in security cameras, and those are really pretty poor quality images with not very good illumination. The cheapest digital camera could do better than that.
Nothing to get excited about.