But the person isn't a cop or security guard (that we know of yet), so if not a LARPing scenario, why the costume?... the costume is disturbing.
IMO, this gives us a Golden State Killer escalating type of scenario no matter how we slice it, as most people who dress up like a security guard would be doing so to blend in; and if you're trying to blend in it seems you would like to get your business over with as soon as possible so you can get on back to your hidey-hole and shed your costume.
So in order to be this casual, IMO the person would have to have been practiced at it; and we haven't heard anything about people in the neighboring community being suspicious of or terrorized by a figure in security gear using it to creepy-crawl all over town yet/before... s/he doesn't seem scared; and to know confidently that being tracked around the church isn't a problem, I would think you would have to be familiar with the church at minimum, and familiar with creeping around like a creep for overarching purposes; so the idea that someone would be all "I think I'll give up the sporting goods store and switch to a church!", still takes some guts on their part.