From: Ask A Rabbi - Jewish.com
(2001) By Rabbi Shraga Simmons
Q: I was told that if a person over 12 is abused by an adult they can not be publicized as an abuser in the Jewish community unless there is another witness. Why is that? what if the abuser is abusing other children? Doesn't the halacha care about those other people being abused?
A: If there is no corroboratory evidence against a person, the person is innocent until proven guilty. If a Bet Din (rabbinical court) will find the person guilty, they will surely notify others, if they deem it necessary. There are exceptions - If it is to stop an evil person from committing unjustified evil to others, when it is difficult or impossible to present it to a Bet Din, before damage is liable to be done. Then if it meets seven conditions, it would be permitted.
In brief, the seven conditions, listed in "Chafetz Chaim" 1:10, are:
1. That the negative aspects you know, should be firsthand information, i.e - what you saw or heard; not from hearsay.
2. You should not conclude in haste that what you saw or heard, is negative. Investigate whether there are extenuating circumstances.
3. You have to first reprove the accused, directly, in a genial manner, before acting upon it.
4. There should be absolutely no exaggeration of the accusations.
5. That you should have the sole intention of helping others; no ill feelings or revenge whatsoever.
6. Seriously try to find a different way (other than speaking evil on this person to anyone), whereby the problem would be resolved otherwise.
7. That not one iota of damage should be done to the person, more than he would have had, had the case been taken to a Bet Din, with the evidence that exists.
Please see "Chafetz Chaim" there, for the elaborate sub-conditions to these seven, before acting.
In your case, the best would be to present the purported evidence to any of the very efficient rabbinical courts. They have the ability to investigate further, and judge the accumulated evidence, whether it warrants further action.