They aren't going to shoot someone for walking out. They wouldn't even shoot someone for standing and heckling during Obama’s speech, although they would probably bum rush them out the door. If they did shoot an unarmed person for doing either one of those things, there would be hell to pay, and a public relations nightmare for the Obama administration, for Notra Dame University, and the Democrat party.
Jumpy secret service. I was just being a little over the top with sarcasm.
The best idea I’ve seen so far is for everyone not planning showing up to not tell the administration.