Caught My Neighbor Watching Me Undress One Night

So last week I was at home getting ready for bed. It's been pretty hot out lately so I wasn't wearing much, just a tank top and shorts. Usually, I keep my blinds closed but that night I had the window open since it felt stifling inside. I started to take off my shirt when suddenly, from across the room, I saw movement in the mirror above my dresser. It took me by surprise, I thought for a moment someone was breaking into my house! But then I realized it couldn't be that since nothing had happened beyond seeing movement out of the corner of my eye. So I turned around slowly and there he was, my neighbor, peeking through my partially open blinds with his hand covering his mouth as if he were shocked to see me. It was Mr. Thompson. He's in his late 30s or early 40s. We've lived next door for a couple years now but mostly we keep to ourselves and just say hello when we run into each other with groceries. Never anything more than that. I don't know how long he had been watching, I felt like I was frozen there, staring back at him as he stared back at me through the glass. The moment stretched out until it got too awkward and I finally spoke up. 'You... you shouldn't do that,' I said firmly but my voice came out softer than I meant for it to. 'I'm sorry,' he mumbled, quickly stepping away from the window before disappearing back into his own house. That was all, the whole exchange took less than a minute. The next day when we crossed paths again at the mailbox, there were obvious signs of discomfort. Mr. Thompson avoided eye contact and seemed extremely on edge around me for weeks after that incident. He'd be as distant as possible but still I couldn't help wondering what was going through his head. Was he thinking about that night over and over? Did it upset him or am I being ridiculous to think there might have been something more nefarious going on? So, do you guys think this was just an innocent mistake and my imagination getting the best of me, or is it possible Mr. Thompson had some kind of ulterior motive in spying on me that way? Let me know what you all think!