The security guard

That's the part that I couldn't figure out. I'm not sure if this was the first night with the cameras or not (I didn't pay that close attention) but it was very soon after they were installed so the only thing we can assume is that the guard was not aware of Hobbs' normal routine so he did not think anything was unusual seeing him come and go. Had it been weeks into the use of the cameras it certainly would have set off some alarms in his head. As it is all new to him it is not too much of a stretch to assume he thought it was all normal. Besides, he didn't strike me as being too bright in the first place.