We had a similar experience in the main park last Friday. We left early because we did not feel safe.
There were groups of unsupervised teens intimidating food vendors and challenging each other. This all stared at about 6pm, up until then things were great. I sat and observed, it seems something KI should do is eliminate the Basketballs as a prize. I overheard some groups of teens, use the term bowling. They were taking the balls and aiming at the feet and legs of park goes trying to trip them and they were successful. Also, bouncing the balls off of kid's heads. I know it's not popular, but I feel a chaperone policy is needed, or don't have the park open past nightfall. When these policies were enacted at Malls, the incidence of violence, improved.