I wonder if they weren't engaged in some destruction of property. . . Most cities that have outlawed skateboarding did so because the kids jump and slide their skateboards down curbs and railings, scratching them up. I've seen kids do this with bikes too, by putting a metal rod on the back wheel that extends a few inches from the axle on either side. They jump the bike, catch it and balance on that rod, and slide down a railing.
Sounds to me like these kids were just doing what most kids typically do---play. Do you think what they were doing warranted the cop to slap cuffs on them and haul them off to jail---shackled---like they had just committed murder or something? Honestly? Where's this cop's sense of proportion?
That very well could be the case.