This sentence appears in Chap 22 of Donna Leon's Acqua Alta:
Er wandte den Blick von der Schale und sah Brett an, versuchte seine Empörung noch einmal nachzuempfinden und ihr verständlich zu machen.
Now, there are 2 people referred to in this sentence, a man and Brett (a woman, BTW). One of these two, in the second part of the sentence, is trying to empathize with the man's indignation and to make it understandable. But I cannot tell who is doing this, which of the two, from the sentence.
The story would be most consistent with Brett, and admittedly, it would be odd for someone to have to try to empathize with his own indignation and make it understandable. That would be the job of another person. But how can the subject of this part be left completely implied? Is it to be expected that German authors may arbitrarily leave out naming a subject they believe should be understood?
If the grammar is accepted as written, the sentence does not appear to make any sense, not from the story line, but more specifically, not from the definition of "nachempfinden" in Duden:
sich so in einen anderen Menschen hineinversetzen, dass man das Gleiche empfindet wie er; etwas, was ein anderer empfindet, in gleicher Weise empfinden (und darum verstehen).
Duden makes it clear that the word requires "einen anderen Menschen", so the man cannot be trying to put himself in his own shoes in order to feel his indignation the same as he feels it himself.
I think it has to be concluded that this sentence has an error. The second part should have specified Brett as the subject, or another word other than "nachempfinden" should have been used.