We live in a complex world and hard as we may try, we have not yet planned and thought out every situation that may occur. Similarly, at a personal level a person will not have experienced or learnt about every possible situation that may occur. We will be faced by new situations, even the most experienced people. Dealing with these situations well will quickly bring a persons behaviour into the "baffled" category, but a failure to deal with it well should be treated with respect and compassion, because the incident has apparently opened an important area in which both the individual and the organisation have something to learn.
What are you correcting
In case of a first time error, the most important thing is that learning takes place, and that the consequences of the error are corrected. What you are looking for is full openness, both on the side of the individual involved ("what did you do when, how and why"), and on the side of the rest of the organization involved ("what were the circumstances, could this have been avoided"). You want to be able to correct the skills, knowledge and training of the person involved, and the conditions and circumstances in the company that have contributed to the situation.
Apparently this is a new case, or seldom appears. The trouble may be that people have difficulty in recognizing the circumstances in which these errors are made. Incidental errors are just that and should be treated like that. To err is human!
Do apply the substitution test (somewhere else on this page). If another individual would have acted the same, then you cannot blame this person, but should rather seek systemic issues.
Another important question to ask is "did the person know, or sense, at the time that this was a new situation which might be beyond his or her experience?". And what was the motivation to continue? Was he or she stuck in the ego-trap?
When looking at management, ask yourself the same question: was this situation new for them, or could they have predicted that this situation would occur. Did they make a mistake, was it a slip or a lapse? Apply the same approach to them.
How are you correcting
Again, the important thing here is that everybody learns from the situation, and that the whole system improves as a result of the situation. Once the lessons are clear, and corrective action has been taken, you may consider publishing the incident in your safety magazine to help others. Make sure that people can and will take notice that nobody will be punished for honest mistakes, as per your Just Culture policy that you (hopefully) adopted.
If somebody acted out of ego, the important thing here is to address that somebody will get more acknowledgement when working to create the best outcome for others, and not by proving oneself to be special.
An important part of this is making sure that the damages caused are corrected and addressed in a just and fair way. If a mistake was made that led to damage, acknowledge it and find a way to correct it. Also communicate about this aspect.
You could consider making a difference for slips/lapses on one side and mistakes on the other side. Mistakes can be more dangerous and possibly could mean that the operator needs more training or coaching in how the system is working and what the appropriate responses are.