Actually, security camera footage would not necessarily be needed – charges could be based on the principal’s account of what happened. Security camera footage of the incident, if it exists, would be corroborating evidence as would any bragging about their threats by any of the three angry male idiots.
That said, I don’t know what charges the evidence would support. Obviously, though, given the statements about the event by the superintendent that have appeared in the media, there should be some public shaming of these idiots. I may be in the minority, but I think the superintendent hit the right tone by not provoking these idiots or their sympathizers more than is necessary. Diffuse the situation – don’t stoke it.