If it was a woman I would try to get her attention and talk to her, if it was a guy I'd capture him with my phone cam, snap a pic get his attention and laugh at him. That's, not all, set up a free tripod account with his picture and license number just for the LULZ. I have to much free time now that school is winding down...
I'd probably just keep on minding my business if it were a dude, and get in on the action if it were a female.