Yes, of course he must be prosecuted if he can be found. As a member of the general population I feel as though it’s possible that a jury wouldn’t convict him and could even find him not guilty. Then he is a free man.
Until his identity is known I shall call him Attaboy Goodman, and if a jury were to convene with me on it, I would be unlikely to take seriously any claim by the state that this vigilantism is somehow more destructive of public order than police murdering and robbing people while ignoring wage theft and corporate crimes.
Unfortunately for many of us Americans, there is a substantial contingent of our government that would really like to do away with public schools.