You don't have to be charged with anything to be arrested. Kennedy's wikipedia page suggests they were released from jail, implying LEO decided they actually committed no crime (and certainly weren't charged). If you're really curious, maybe the jurisdiction has public arrest records, but this assumes that the cops were doing everything by the book, which is not always an apt assumption.

My guess is that towns and leo get, let's say, passionate, when a big tourism draw gets defaced, or when something can get more dangerous, but cooler heads eventually prevailed.