I've been to dozens of stadiums, and yes they have security cameras that can zero in on an unruly fan, and some even have jails, but snipers?
Even Chicago and Philly don't have those. Snipers, I mean.
Perhaps I shouldn't have spoken for other stadiums.....I have a friend who worked security at Ford field who told me that every game day a squad of Detroit police officers would arrive early with their rifles then strategically position themselves around the upper rim.....