What is obligatory to do regarding a non-Muslim colleague who committed fraud and exploited his position, knowing that the head of the company is trying to protect him, and is speaking about his deed publicly considered blameworthy gloating?

The swindler deserves punishment and is obligated to return what he took unjustly. His case must be presented to the judicial authority. It is not permissible to expose him unless he is openly defiant and reckless, or if there is fear that he might involve others in swindling and fraud. This is because the recommended concealment applies to respectable individuals and those like them who are not known for harm and corruption. As for those known for such actions, it is preferable not to conceal their deeds; instead, their case should be brought before the ruler. It is not permissible to harm a non-Muslim or make them hear what they dislike, because Islamic law has protected their honor, blood, and property.