David Ferrera, a veteran teacher and assistant football coach, published an explosive letter accusing union leaders of bullying, shunning, and vandalism against members who didn't tow the party line.
In one part of the letter he says, "Individuals have had damage done to their personal property. They have received written threats and incidents of bullying during the day."
Ferrara claims his own car was vandalized in the school parking lot.
He also claims in the letter that "Elected union officials promote, support and are willing to use terror and fear to stay in power."
In the aftermath of the letter, the school board president is calling on police to investigate.
"We've heard of cars being keyed, we've heard of tires being slashed, we've heard of windows being broken but we never had anyone brave enough to come forward until now," said Ritchie Webb.
Ferrara was at Neshaminy High School Friday going about his normal classroom duties but refused to speak with Action News on camera about the accusations.
Union critic Larry Pastor claims he wants the FBI to probe for possible racketeering.
"Many of us after reading his letter thought that this warranted an investigation because if it is organized and methodical, that is really a direct violation of our laws," said Pastor.
The National Federation of Teachers issued a written statement, calling Ferrara's letter no surprise because he is a constant critic of union leadership.
Addressing the accusations, part of the statement read "We absolutely do not condone any form of vandalism, violence or intimidation against anyone."
As for the on-going contract dispute itself, non-binding arbitration is the next step in the increasingly bitter stalemate.