I was also at this performance and it was definitely not a publicity stunt. I was sitting in front of the guy's seat who jumped on the stage. He was there with what I assume were his similarly aged brothers and mother. I'm assuming they were the ones who were filming him do it based on the camera angle. The ushers came over to their group after they yelled at him and asked him to leave. Their mother stood up and said "Please, please, he's my son don't make us leave." After she pleaded some more, the usher said, "If it happens again I'm calling the police." Then when the usher left, they all laughed. Based on the comments they made during the show their mother made them come to the theater that night and they thought it was hilarious that he got into trouble....
The whole thing made me feel crazy!
Fun fact...Julia Stiles was also in the audience that night.