I am sure he was, and I am sure he molested many others, and I am sure that there were people that knew and hushed it.
Whether this was the case here or not, there are certainly people like Levi Aron who are free because people have done exactly that: Hushed up cases of abuse, molestation, and the like. This needs to end, once and for all.
As R' Adlerstein says:
It is time to forever bury the myth that reports of pedophilia can be managed and dealt with by committees of rabbonim, even for a short time. It is time to bury the myth that there is a serious halachic barrier to going to authorities to deal with credible reports of such behavior. Enough baalei halacha have told us that there is no barrier.
Choshen Mishpat 358:12 tells us that those who vex the public can be handed over. Any pedophile does at least that, and poses a danger of doing much more. Moreover, mesirah of a molester exposes him to a safek of danger; pedophiles pose a much greater danger level to many more victims.
It is natural and good that many people were not eager to rush to modes of address that themselves could be too sweeping and harsh, with terrible consequences to people and their families. They thought that various types of modus vivendi were possible. By now they should realize that this is not true. Rabbonim cannot handle the issue. We have enough evidence of this. Failure to take notice of this could have been said, figuratively, to be shefichas damim/ bloodshed.
Today, it is no longer figurative.
It is not a stain on our record that it took time to learn the facts about molestation. Reacting far too slowly is a terrible stain, though.
Leiby’s horrific petirah can save the lives of many others – those who could meet a similar fate, r”l, and those victims whose lives are a living death.
I may still be proven wrong, but the analysis will not change. Parents will be speaking about safety to their children. Whatever really happened to Leiby, the fact is that our kids are often in far greater [sic: danger] in school, shul and camp than from encounters with detested “others” while walking home.
The greatest aliyah for Leiby and nechamah for his family will come from all of us getting serious about molestation.
If your rov doesn’t get it, think of getting a new rov.