Where was the detail? Was one provided? Was one paid for?
From what I hear there was one armed security guard.
As someone who organized such events in the past, I can tell you it’s up to the pol and his/her event organizers to arrange for security, private or public law enforcement. I’ve read that Rep. Giffords didn’t want a law enforcement presence. Many members of Congress don’t want to pay for their own security details, but law enforcement in most jurisdictions will provide it for such events if asked.