The whole problem with your hypothesis is that they weren't cops! They were security officers. No power to arrest.
And who told you that? This article says they were police. Why else is the Mayor of Chicago bitching about the incident?
Mayor Rahm Emanuel said the suspension of the three officers were handled well by Aviation Commissioner Ginger Evans.
So now i've provided some evidence that they were police, so you go ahead and counter it with some evidence that they weren't.
Then we can figure out which one is true and which isn't.