If I was that guy, I would have shook your hand after you escorted me off the property. It sucks some people just don't have common sense. A local hospital has hospital police, they drive nice jeeps equipped with the lights, markings an all the jazz.
You did more than you had to to help the guy out and instead of being smart his dumb ass went and got himself arrested.. Don't be surprised it you get served papers in the near future.