Empathy is the ability to put yourself in someone's shoes. The sentence “What happened had to happen as it happened” also helps. In the past, people had to be what they were - and must be who they are in the present. The more empathy you have, the better you can understand the other person.
At the same time, the other person will usually become more open when he feels so that he can be understood.
The respective goals* are decisive. If one is empathic, then the goal is to understand the other person in their being, to put oneself in their shoes.
It is another matter whether you find the other person sympathetic.
To say "what happens must happen how it happens" does not mean that you approve of everything the other person did. It just says that what happened had to happen as it happened.
All human emotions and feelings in one are still there. Only they are more or less relativized by the knowledge that everything had to happen as it happened.
Of course I would never approve of murder or similar crimes. But I know that everything had to happen as it happened. Accordingly, my reactions and judgments are more tolerant.
Tolerance means that you have to endure or have to endure what happened, also because you cannot change the past. Tolerance also means that you shouldn't take revenge blindly. And that you should possibly be considerate. Respect in the literal sense; that you look back on the past.
The ideal would be to punish the perpetrator only to the extent that he or someone else does not do this again. But since we are all human beings, with our feelings and emotions, our values and attitudes, this ideal is often not achieved.
And one more word: It is not that you are not free in your actions and decisions. - However: Of course, one cannot be free in the true sense, because: what happened had to happen as it happened.
On the other hand, you are free to make decisions about the present and the future because you don't know what needs to happen.