Here is my biggest problem with all the speculation about him being an undercover officer:
Why, then, is Hannah Graham missing?
It does not compute.
Its just speculation on my part, but I doubt any of the people (except the perp) who saw Hannah that evening, in the bar, on the street, on the Mall, realized she was in eminent danger of being kidnapped or about to disappear under mysterious circumstances. To most people she probably looked like just another tipsy co-ed, a rather common sight in that area.