They were probably the quiet guy sitting by himself in the fifth row of chairs. They might even have helped set up the sound system.
OTOH, the INS might like to know about this guy, and your local State Department office. Activities inconsistent, don't y'know.
I remember in the turbulent early 70s two guys plotted to break into the local draft board and one of them was an undercover cop. Although I have no sympathy for the fool who planned this destruction of govt. property, I still wonder if he would have planned it on his own.