It is extremely unlikely that these officers will face criminal charges. The police are generally immune from such prosecution unless it is obvious that they know they are violating someone's rights.
Very few people ever carry openly in urban areas in and it unfortunately does not surprise me that some if not many officers don't know that open carry is legal there.
It is definitely not fair that being unaware of the law is not an excuse for citizens, but is an accepted excuse to some extent for the police.
However, there really is no fair way to address this when the government has made the legal system so excessively complicated.
The people in charge of our police departments are politicians, and the training they receive is at times politically skewed.
The police has the task of enforcing the laws, however since the laws are at times excessively complex and even contradictory at times, it is likely that they will screw up sooner or later even if they are honorable people doing their best.
Therefore these people will have to seek justice in civil court this time. If these officers do this again, the excuse that they honestly didn't know isn't credible, and they might lose their immunity from prosecution if you can find a prosecutor who will actually charge them with a crime.
Please see my post 120. It is neither expressly legal, nor illegal, to open carry in this state.