There has to be a better way to handle these situations. For example, everyone that goes through security gets some sort of stamp or something to indicate they’ve been through and cleared. They show it at the gate and if this sort of thing happens, they check people who are already on planes or in the gate area. No stamp (or whatever), then escort that ONE person off the plane. This is absolutley absurd!
The simpler solution used by airports I've been in is to post a security guard at the exit points whose sole and undoubtedly mind-numbingly boring job is to dissuade anyone from trying to re-enter the sterile area.
I have to wonder at the quality and positioning of their video cameras in Newark that they couldn't just lock down the terminal, print a screen shot, and walk through the terminal until someone recognized the guy's face.