You can see he looks apprehensive, stressed right here. And it’s because he hears a siren, presumably police. He’s on high alert because he’s just waiting for the day that those sirens come for him.
And here he is after the (police) car with the siren passes by him. He’s relieved, a little shaken. He swallows, breathes, and gathers himself a little.
ANNNDDD then he spots the guy across the street who’s staring at him, and you can see his stomach drop and he visibly tenses again. It’s a nightmare come to life. And I’m saying “a nightmare” because sadly, this probably isn’t his worst nightmare.
And his breathing picks up, and he looks so afraid, his tiny bit of peace, whatever peace he can get, is shattered. He always knew this day would come, but he had hoped he’d have more time. And it breaks my fucking heart.
And I have to say biiiiiggg KUDOS to Sebastian Stan for acting out all the minutiae of Bucky’s facial expressions and body language. Because HOLY SHIT there was a lot of stuff going on in Bucky’s internal monologue.