First, I can't speak to the laws of Maine but in some states you are allowed to open carry on your own private property. 
  
Secondly, I agree in that the police only received a call stating there was an individual with a gun.  Whether that is true or not, they will respond accordingly, as they did.  As you stated, he wasn't charged and he's not even cuffed in the photograph so I don't see what all the fuss is about; but considering the news this morning reported about some kid who didn't get a foul ball at a baseball game, I can only guess it was a slow news day! 
  
Lastly, the tattoo is not against the laws, unless we're talking about the laws of good taste!  But one look at that guy and I would say he has a history of bad choices.  Even the look on the deputy's face tells he's also thinking what a douchebag this guy is! 
  
Cheers!  M2