As satisfying – necessary, even – as it is to have heads roll when a tragedy strikes that clearly, or even just possibly, could have been avoided, it is just as frustrating when all the right steps were taken, when protocol was followed and yet …

It would appear, at least this early into the investigation, that Joshua Wairi, the 27-year-old who taught in several Somerville elementary schools over the last several years before being arrested this month on child pornography possession and distribution charges, was checked out before being hired both in Somerville and Cambridge, where he was working as a teacher at the time of his arrest.

A background check won’t find anything if there’s nothing to find, and that seems to be the case here. No arrests, no suggestion then of what is being alleged now, no red flags at all.

What is not as clear are the details surrounding Wairi’s admission, according to authorities, that he recorded children changing in a locker room. The when and where have yet to be revealed. That information will shed light on if procedures weren’t followed if the recording was done in a setting where another adult should have been present as a matter of procedure.

While investigations require discretion, and not every piece of information can be made public straight away, parents of children who may have been recorded – and their images subsequently shared with strangers online – should be informed as soon as logistically and legally possible whether they have reason to be more than just disgusted at the criminal betrayal of trust revealed in Wairi’s arrest.