Random Encounter at the Store

I’d like some analysis and feedback - curious to know if I handled the situation appropriately.

Stopped by my local pharmacy to pick up some vitamins. When I turned down an aisle towards the cash register I notice a man staring seemingly at me. His eyes are wide and somewhat bewildered. His whole body was also fully facing me, which was odd considering he was at the cash register.

At first I look away and then do a double take because it honestly caught me off guard and wanted to know if maybe he recognized me. By that point his expression seemed to soften but was turning towards the person next to him - a female companion. She was looking at him and then at me.

Seeing her made me immediately disengage. Because frankly I want to be part of no mess (just in case). I ignored me the rest of the time there and even left a little extra space between myself and them. Zero eye contact even though it felt incredibly awkward while they finished their business at the register.

It left me a little curious and part of me wants to know what happened and if maybe I should have observed longer for the sake of closure.

What do you think happened and what should I have done differently?