Very simple to say the are "investigating" the incident and going forward they will have security for the officials, additionally they should say they are working with the parents, students, parent associations etc to address the issue of treatment of officials and remind fans they have a zero tolerance policy and parents may be ejected or banned from games going forward.
Essentially make it look like they care but not be forced to do anything this game....or kick the can a few weeks (or season) and hope people forget about it.
I know nothing and have no dog in this fight, but I would try this as a first step.
If the allegations are true the fan should be punished and the school (if they are protecting them) should be punished too.