Adult bullies.
Sounds to me like the principal is making terrorist threats on the Internet.
“I am coming for you”
If he had consulted his lawyer or the school district's solicitor, he would have been informed that he has no authority to take any action for the exercise of free speech that occurs outside of school unless the activity results in a substantial disruption during school hours.
And he would also have been informed that "cyber bullying" does not usually meet that standard.